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Oncotarget, 2018, Vol. 9, (No. 69), pp: 33232-33243
Research Paper
Prevalence of MDM2 amplification and coalterations in 523
advanced cancer patients in the MD Anderson phase 1 clinic
Vikas Dembla1, Neeta Somaiah2, Pedro Barata3, Kenneth Hess4, Siqing Fu1, Filip
Janku1, Daniel D. Karp1, Aung Naing1, Sarina Anne Piha-Paul1, Vivek Subbiah1,
Apostolia M. Tsimberidou1, Kenna Shaw5, Funda Meric-Bernstam1 and David S.
Hong1
1
Department of Investigational Cancer Therapeutics (Phase 1 Program), The University of Texas MD Anderson Cancer Center,
Houston, Texas, USA
2
Department of Sarcoma Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
3
Department of Solid Tumors, Taussig Cancer Institute, Cleveland Clinic, Cleveland, Ohio, USA
4
Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
5
Sheikh Khalifa Bin Zayed Al Nahyan Institute for Personalized Cancer Therapy, The University of Texas MD Anderson Cancer
Center, Houston, Texas, USA
Correspondence to: David S. Hong, email: dshong@mdanderson.org
Keywords: MDM2 amplification; phase I trials; solid tumors; TP53 mutation; CDK4 amplification
Received: January 04, 2018
Accepted: August 20, 2018
Published: September 04, 2018
Copyright: Dembla et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License
3.0 (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and
source are credited.
ABSTRACT
Background: TP53 is the most commonly mutated gene in cancer and codes for
the best studied tumor suppressor, p53. MDM2 is involved in the negative regulation
of p53 and itself serves as an oncogene, reported to be overexpressed in several
cancer tumor types. In this retrospective study, we assessed the occurrence of MDM2
amplification among patients with various types of cancers and its association with
clinical factors, other genetic aberrations, and response to targeted therapy in a phase
I clinical trial setting.
Methods: Samples from patients with advanced solid tumors who had been
referred to the MD Anderson phase I clinical trials program between January
2011 and January 2016 were collected and analyzed for MDM2 amplification using
FoundationOne’s genomic profiling assay. Patients whose tumors expressed MDM2
amplification were compared to those with tumors of the same histologic types
without MDM2 amplification.
Results: We tested tumors from 523 patients, of which 23 (4.4%) had MDM2
amplification. The highest prevalence of MDM2 amplification was in sarcoma (57%),
breast cancer (13%) and bladder cancer (9%). Six patients with liposarcoma were
treated on phase I protocol with an MDM2 inhibitor. The most common molecular
aberrations co-occurring with MDM2 amplification was CDK4 amplification (70%).
TP53 mutation was also detected in 7 patients (30%).
Conclusion: MDM2 amplification was most commonly associated with
liposarcoma. Concomitant alterations in additional genes such as CDK4 amplification
and TP53 mutations, along with variable responses to targeted therapies including
MDM2 inhibitors, suggest that further combinational studies are needed to target
this population.
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and help establish criteria for selection of patients most
likely to benefit from them. We therefore embarked on
this retrospective study to assess the relationship between
MDM2 amplification and the clinical, pathologic and
genetic characteristics of this MDM2-amplified patient
population as well as their response to an MDM2 inhibitor
in phase I trials, and from these provide a basis for further
studies of the clinical role of MDM2 inhibitors.
INTRODUCTION
The tumor protein p53 (hereafter, p53) is one of the
most studied tumor suppressors, with TP53 being the most
frequently mutated gene in cancer [1]. The p53 pathway is
responsible for sequence-specific transcriptional activation
(both in vivo and in vitro)[2, 3] and perturbations to this
pathway are present during the development of most
cancers [4]. Since p53 currently cannot be directly targeted
by drugs, the focus of therapeutic strategies instead is on
negative regulators of the TP53 gene.
The murine double minute 2 (MDM2) gene was
originally described in a tumorigenic mouse cell line
because of its amplification [5, 6]. The human homolog
of MDM2 is mapped to chromosome 12q13-15 region
[7, 8]. MDM2’s interaction with p53 and its negative
regulation of p53 function was found to be mediated
through two different mechanisms: 1) the direct binding
of MDM2 to the N-terminal of p53, which subsequently
inhibits the transcriptional activation function of p53,
and 2) its activity as an E3 ubiquitin ligase, which targets
p53 and facilitates its degradation through the 26S
proteasome [9–11].
As a key negative regulator of p53 expression,
MDM2 is thought to function as a proto-oncogene in
preventing the accumulation of activated p53 [12].
This was verified in early studies showing MDM2
overexpression in soft tissue sarcomas which was mutually
exclusive with the occurrence of p53 mutations [13].
MDM2 overexpression has since been reported in a variety
of human tumors, mediated by either gene amplification
or other mechanisms that remain unknown [14]. MDM2 is
known to be amplified or overexpressed in 40% to 60%
of human sarcomas as well as in several other solid and
hematological malignancies [15, 16]. Some tumors that
overexpress MDM2 also express wild-type p53, which is
inactivated upon its interaction with MDM2 [17]. MDM2
overexpression may be related to an increased likelihood
of distant metastasis, decreased response to treatment, and
poor clinical prognosis [14].
For these reasons, MDM2 has posed as an
attractive and relevant target for cancer therapy. One
strategy to promote p53 expression is to inhibit MDM2,
since blocking the specific interaction between MDM2
and p53 would generate high levels of wild-type p53
and trigger apoptosis [18]. Releasing p53 may then
contribute to cellular growth arrest and apoptosis. With
this rationale, different MDM2-inhibiting molecules have
been developed in recent years, and clinical trials of these
agents are ongoing [15, 19].
Despite extensive data on MDM2 dysregulation
in cancer, little is known about the characteristics of
patients in whom MDM2 gene expression is altered or
amplified. With the emergence of MDM2 inhibitors, an
understanding of this particular patient population would
provide a better rationale for the use of these inhibitors
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RESULTS
We identified 523 patients who had undergone
FoundationOne testing for MDM2 amplification and
whose results were available for analysis. Of these, 23
(4.4%) had MDM2 amplification in their tumor. As a
comparison dataset, we identified another 124 of the 523
patients whose tumors did not have MDM2 amplification
or MDM2 alterations but were of the same histologic types
as those of the 23 MDM2-amplified patients. Selected
demographic, diagnostic, and genetic characteristics of
these two patient groups are summarized in Table 1.
The highest prevalence of MDM2 amplification
by histologic type was found in sarcoma patients (13
of 33 = 39% vs 10 of 114 non-sarcoma patients = 9%;
p < 0.0001); the second highest was found in patients
with metastatic breast cancer (3 of 56 = 5.3% vs 20 of
91 = 22%; p = 0.0071). Of the 13 sarcoma cases with
MDM2 amplification, liposarcoma was the most common
histologic subtype (9 patients). The histologic subtypes,
number of metastasis sites, performance status, and prior
lines of therapy are summarized in Table 2. DNA samples
were obtained for Foundation Medicine testing from all
523 patients prior to starting therapy.
The median albumin level was 4.1 g/dL (normal,
3.5 to 4.7 g/dL); the median lactate dehydrogenase level
was 497 U/L (normal, 313 to 618 U/L); and the median
number of metastatic sites was 2. The most common site of
metastasis were the lungs (n = 57), followed by the bones
(n = 48) and liver (n = 41). We also determined the Royal
Marsden Hospital (RMH) score for patients included
in our analysis (Table 1), with the exception of four (4)
patients in the non-MDM2 amplified group. This score is
used to predict patient survival in phase I clinical trials; a
lower score is generally associated with longer survival
[20]. Among the 23 patients with MDM2 amplification,
11 had an RMH score of 0 with a median overall survival
(OS) was 24 months, which was significantly longer than
the median OS of 6 months among the 12 patients who
had an RMH score > 0 (hazard ratio [HR], 3.6; confidence
interval [CI], 1.1, 11.5; p = 0.031). Among the non-MDM2
amplified patients, 67 had an RMH score of 0 while the
remaining patients had an RMH score > 0 ([HR] for
MDM2 amplification adjusted for RMH = 0.6; [CI], 0.4,
1.1; p=0.13).
Sixteen of the 23 patients with MDM2 amplification
were noted to have co-occurrence of CDK4 amplification,
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Table 1: Patient characteristics and RMH score
MDM2
NOT Amplified
N = 124
p-value
All Patients
MDM2
Amplified
N = 23
Mean Age
56 years
58 years
55 years
0.084a
Sex, n (%)
Female
Male
10 (43)
13 (57)
75 (60)
49 (40)
0.13
Race, n (%)
White
Black
Other
Missing
20 (87)
2 (9)
1 (4)
0
96 (81)
12 (10)
11 (9)
5
0.71
Tumor Type, n (%)
Sarcoma
Breast
Bladder
Liver
Lung
Salivary
Kidney
CUP
13 (57)
3 (13)
2 (9)
1 (4)
1 (4)
1 (<1)
1 (<1)
1 (<1)
20 (16)
53 (43)
8 (6)
23 (19)
10 (8)
3 (<1)
3 (<1)
4 (<1)
<0.0001
0.0071
0.69
0.13
1
Aberrations, n (%)
CDK4
CDKN2A/B
MYC
PIK3CA
PTEN
CCND1
TP53
16 (70)
5 (22)
5 (22)
1 (4)
0 (0)
1 (4)
7 (30)
2 (2)
6 (5)
21 (17)
19 (15)
16 (13)
13 (10)
58 (47)
<0.0001
0.015b
0.56
0.2
0.077
0.7
0.15c
0
1
2,3
11
8
4
67
41
13
0.42
Variable
RMH Score
Level
Abbreviations: RMH, Royal Marsden Hospital score; CUP, carcinoma of unknown primary. RMH score could not be
calculated in 4 patients in MDM2 not amplified group.
a
calculated using Wilcoxon rank sum test; b calculated using Fisher exact test. c calculated using chi-squared test.
cancer not otherwise specified (NOS), adenocarcinoma
of the lung, soft tissue liposarcoma, squamous cell
carcinoma of unknown primary, and bladder urothelial
carcinoma. MYC amplification was observed in patients
with invasive breast carcinoma (2), breast carcinoma
NOS (1), Ewing sarcoma (1), and bladder urothelial
carcinoma (1). TP53 mutation was seen in one patient
each with kidney urothelial carcinoma, Ewing sarcoma,
five had CDKN2A/B loss, and five had MYC amplification.
Other aberrations that co-occurred with MDM2
amplification in this analysis include mutations in
TP53 (7 patients), PIK3CA mutation (1), and CCND1
amplification (1). Among the aberrations co-observed,
CDK4 amplification was most commonly noted in
patients with soft tissue liposarcoma (9 of 16 patients), and
CDKN2A/B loss was seen in one patient each with breast
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Table 2: Histologic characteristics and status of patients according to MDM2 amplification status
MDM2 amplified
(n = 23)
MDM2 not amplified
(n = 124)
0
0
1
1
6
42
2
9
53
3
5
23
4
3
5
0
2
6
1
19
116
2
2
2
0
2
NA
1
4
NA
2
7
NA
3
7
NA
4
1
NA
5
0
NA
6
2
NA
Liposarcoma
9
1
Osteosarcoma
2
11
Ewing sarcoma
1
4
Rhabdomyosarcoma NOS
1
4
Invasive Ductal carcinoma
2
32
NOS
1
14
Metaplastic
0
6
Adenocarcinoma
0
1
BLADDER CANCER
(Urothelial carcinoma)
2
8
Variable
No. of metastatic sites
ECOG Status
No. of prior lines of therapy
Histologic Subtypes
SARCOMA
BREAST CANCER
(Continued )
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MDM2 amplified
(n = 23)
MDM2 not amplified
(n = 124)
KIDNEY CANCER (Urothelial
carcinoma)
1
3
UNKNOWN PRIMARY (Squamous
Cell carcinoma)
1
4
Adenocarcinoma
1
9
NOS
0
1
Adenocarcinoma NOS
1
2
Adenoid cystic carcinoma
0
1
Hepatocellular carcinoma
1
19
Fibrolamellar
0
4
Variable
LUNG CANCER
SALIVARY GLAND CANCER
LIVER CANCER
Abbreviations: ECOG, Eastern Cooperative Oncology Group; NOS, not otherwise specified; NA, not applicable.
soft tissue liposarcoma, invasive ductal carcinoma of the
breast, breast carcinoma NOS, hepatocellular carcinoma,
and salivary adenocarcinoma NOS. No TP53 mutation
was noted in two patients with MDM2 amplified bladder
cancer.
For the 23 patients with MDM2 amplification, we
determined the copy numbers (CNs), as determined via
next-generation sequencing by FoundationOne: total,
6-150 CNs; mean, 30.39; and median, 16. The highest
CNs were in patients with soft tissue liposarcoma (29-150
CNs). The lowest were in patients with liver cancer (6
CNs), unknown primary cancer (7 CNs), breast cancer (7
CNs), and lung cancer (9 CNs).
Of the three breast cancer cases, two were estrogen
receptor (ER)-positive, but were progesterone receptornegative. One of the two ER-positive tumors also had
Her2 amplification (by fluorescence in situ hybridization).
Two of the three tumors had TP53 mutation, and all three
had MYC amplification.
As shown in Figure 1, the median OS in patients
with MDM2 amplification was 13.6 months versus 10.6
months in patients without amplification (p = 0.12).
Survival duration could not be accurately determined
for one patient without MDM2 amplification; hence,
the median OS is reported for 123 patients. The median
overall age was 56 years (range = 15-81 years); the median
age of patients with MDM2 amplification was 58 years
(range = 23-77 years); and the median age of patients
without MDM2 amplification was 55 years (range = 15-81
years). In a Cox proportional hazard model with age > 60
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years, the adjusted hazard ratio for MDM2 amplification
was 0.59 (range = 0.33-1.04; p = 0.068), and the adjusted
hazard ratio for age > 60 years was 1.50 (range = 1.012.24; p = 0.045). Of the 124 patients without MDM2
amplification, 53 (43%) patients had breast cancer while
of the 23 patients with MDM2 amplification, 3 (13%)
had breast cancer; the Fisher exact test p-value for breast
cancer was 0.0090. The p-values for the co-amplifications
were also Fisher exact test p-values and therefore valid for
small numbers. The median follow-up period in all 147
patients was 28.3 months, with 104 deaths observed.
Six of the 23 patients with MDM2 amplification
were enrolled in a trial involving an MDM2 inhibitor. All
six patients had liposarcoma. There was a partial response
in three patients and stable disease in two patients (15.7
months and 4.7 months). The sixth patient was still on trial
at the time of this analysis. TP53 mutation was noted in
one of these six patients (this patient had enrolled prior to
the availability of FoundationOne results). None of the 23
patients with MDM2 amplification was treated with prior
immunotherapy.
DISCUSSION
To our knowledge, this study is the largest analysis
of MDM2 amplification in solid tumors reported in the
current literature. We found a low incidence (4.4%) of
MDM2 amplification among 523 patients whose solid
tumors were sent for next-generation sequencing testing
with Foundation One. MDM2 amplification was most
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NCT02343172 and NCT01692496). Both of these trials
are in liposarcoma patients, not breast cancer patients.
Grünewald et al [24] reported co-expression of CDK4
amplification with MDM2 amplification in one patient
with salivary duct carcinoma. In another analysis, Roshida
et al [25] reported an overall co-occurrence rate of 6.5%
in 107 osteosarcoma patients whose tumors were tested
for MDM2/CDK4 amplification. This co-occurrence was
associated with a low grade of osteosarcoma.
The significance of our study lies in the larger
number of patients tested for MDM2 amplification in
our analysis compared to what has been previously
reported. Previous studies report an incidence of
MDM2 amplification from 0% to 6.3%[26]. In our
study, we report 4.4%, which is consistent with earlier
reported studies. Interestingly, all six patients who were
enrolled in an MDM2 inhibitor trial in our study had
liposarcoma. The best response was a partial response
in three patients and stable disease in two patients; the
sixth patient was still undergoing therapy on a trial at the
time of the analysis. It is difficult to make comparisons
given our small numbers of liposarcoma patients but
these results compare favorably to prior data from
Livingston et al [27].
While the number of patients with MDM2
amplification was too small to be meaningful in our
frequent in patients with liposarcoma, followed by patients
with metastatic breast cancer. Other aberrations that
most frequently co-occurred with MDM2 amplification
were CDK4 amplification, CDKN2A/B loss, and MYC
amplification. Concomitant alterations of MDM2 and
CDK4 are known and have been described in liposarcoma
[8, 21, 22]. Previous studies have suggested that the
presence of neochromosomes in cancer and sarcoma
in particular, could explain the mechanism of MDM2
amplification in these tumors. Neochromosomes, which
are extra chromosomal structures that harbor oncogenes
at high copy numbers, could incorporate Chr12q
fragments including MDM2, and drive tumorigenesis
[23]. Interestingly, we also found that TP53 mutations and
MDM2 amplification were not mutually exclusive in our
analysis.
Given the prevalence of co-occurrence of MDM2/
CDK4 amplification, targeting tumors that harbor these
aberrations, combination therapy incorporating inhibitors
of these two amplifications is an attractive proposition.
Among the six patients with liposarcoma, histology was
noted to be atypical lipomatous tumor in three patients
and dedifferentiated liposarcoma in the remaining three
patients. Currently, there are only two clinical trials
evaluating the combination of an MDM2 inhibitor
and a CDK4 inhibitor (ClinicalTrials.gov identifiers
Figure 1: Overall survival according to MDM2 amplification status: After adjusting for RMH score, OS with MDM2
amplification = 13.6 months vs OS without MDM2 amplification= 10.6 months, hazard ratio = 0.6, confidence interval
(CI) = (0.4, 1.1); p = 0.12. The median refers to months of survival.
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described in the literature [37, 39–42]. Florenes et al
[39] related MDM2 amplification to TP53 status. MDM2
amplification was noted in ten tumors (10.3%), while
TP53 mutation was noted in 12. However, only one case
had both TP53 mutation and high levels of MDM2 mRNA.
In a study by Cordon-Cardo et al [40], 211 adult soft tissue
sarcomas were studied to detect molecular abnormalities
of TP53 and MDM2 expression. Monoclonal antibodies
directed against MDM2 and p53 proteins were used
to measure their overexpression. Strikingly, 22 cases
had high levels of both p53 and MDM2 proteins on the
basis of immuno-reactivity; this finding was statistically
significant (p < 0.05) and associated with poor survival.
However, overexpression of MDM2 and p53 proteins in
the nuclei of tumor cells is not correlated with MDM2 gene
amplification or TP53 mutation. Co-occurrence of MDM2
amplification and TP53 mutation was also noted in two
patients by Grünewald et al [24]as well. Drummond et al
[42] reported that TP53 mutant, MDM2 amplified cell lines
that were resistant to MDM2 inhibitors retain sensitivity
to ionizing radiation and suggested that such patients may
have alternative treatment options like radiation therapy.
Saiki et al [43] demonstrated that MDM2 amplification
and TP53 mutation are not mutually exclusive in tumor
cell lines, possibly because of a misidentified TP53
mutation or heterozygous TP53 mutation or because cell
lines harbor viral gene sequences known to inactivate
p53. It is also possible that MDM2 affects p53 in a dosedependent manner, and only tumors that carry high copy
numbers of the MDM2 gene express enough protein to
inhibit p53 [41]. Co-existence of both these aberrations
should also be expected if both events are independent of
each other. On the basis of this observation and our results
which also showed that MDM2 amplification and TP53
mutations are not mutually exclusive in advanced cancers,
alteration in one gene should not preclude testing for the
other. It is important to check for the TP53 mutation status
once MDM2 amplification has been reported in a nextgeneration sequencing test.
The reported incidence of MDM2 amplification
in various series conducted in single tumor types (0%
to 6.3%) is consistent with our findings [24, 26, 44,
45]. Grünewald et al [24], in a series of 51 patients with
salivary duct carcinomas, reported MDM2 amplification in
three patients (5.8%), as well as synchronous CDK4 and
MDM2 amplification in one patient with a co-expression
rate of 33.3%. We observed a higher co-expression rate
in our study (16 of 23 [(70%]). In addition, our analysis
included a much larger patient cohort. Michalk et al [26]
reported a 6.3% incidence of MDM2 amplification in
esophageal carcinomas (adenocarcinoma and squamous
cell carcinoma), and Schoolmeester et al [44] found an
incidence of 5% (2 of 43 cases) in endometrial stromal
tumors. In contrast, Lyle et al [45] found no MDM2
amplification in their series of ten tests among 38
patients with malignant phyllodes tumor of the breast.
analysis, there was a trend toward longer OS in the 23
patients whose tumors had MDM2 amplification.
Three of the 23 (13%) patients with MDM2
amplification had a diagnosis of metastatic breast cancer.
Despite the high percentage in this very limited series,
two of these three patients harbored mutant TP53 and
therefore were not eligible for enrollment in trials
involving an MDM2 inhibitor. Most MDM2 inhibitors
under development target the MDM2-p53 complex,
including Nutlin-3 [18], RITA [28], MI-219 [29],
AMG232 [30], and SAR405838 [31]. These inhibitors
have little or no effect on cancers with mutant TP53.
Selective inhibitors of ubiquitin-specific protease-7
(USP7) such as GNE-6640 and GNE-6776 are also being
studied as potential stabilizers of p53 via MDM2 [32].
USP7 regulates stability of p53 tumor suppressor and
other proteins necessary for tumor cell survival. GNE6640 and GNE-6776-like molecules induce tumor cell
death and enhance cytotoxicity with chemotherapeutic
agents and targeted compounds. This strategy may be
broadened for developing other deubiquitinase inhibitors
to inhibit proteins that require ubiquitin binding for full
functional activity. Chrisanthar et al [33] reported that
patients with stage III breast cancer with the MDM2
SNP309 genotype did not experience a response to either
epirubicin or paclitaxel. The frequency of mutant TP53
in breast cancer has been reported to be 30% to 73%,
but it fluctuates widely between subclasses of breast
cancer [34, 35]. As a result, MDM2 inhibitors have no
significant anticancer activity in such tumors. Therefore,
new strategies to target MDM2 are needed. Indeed, new
studies are underway to develop a new class of MDM2
inhibitors that exhibit anticancer activity, regardless of the
tumor’s p53 status [36].
One very interesting finding in our analysis was
the presence of mutant TP53 in seven patients. This
was not significantly different from the rate in patients
without MDM2 amplification (30% vs 47%, p=0.15).
Nonetheless, the co-existence of mutant TP53 with MDM2
amplification is surprising, as they have been thought to
be alternative mechanisms for inactivating the suppressing
cell growth pathway and thus mutually exclusive [37]. A
recent study by Sanchez-Vega et al [38] reports the mutual
exclusivity of TP53 mutations and MDM2 amplification
in tumors profiled by The Cancer Genome Atlas (TCGA).
The discrepancy between our results and this recent report
may be largely due to the nature of TCGA curated samples
which are largely from primary tumors, whereas our study
includes metastatic tumor samples from heavily pretreated
patients.
Tumors with mutant TP53 are canonically thought
to not respond to MDM2 inhibition. Our analysis clearly
shows that this is not a mutually exclusive phenomenon
and that subsets of patients with MDM2 amplification
also have a co-existing mutant TP53. This conflicting
observation is uncommon but definitely has been
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Zhu et al [46] reported the first documented cases of
MDM2 amplification in laryngeal and hypopharyngeal
liposarcoma. In a separate study by Kato et al [47], MDM2
has been recognized as a marker of pseudo-progression
in patients treated with single-agent checkpoint (PD-1/
PDL-1) inhibitors. None of the 23 patients with MDM2
amplification in our analysis was treated with prior
immunotherapy as of the cut-off date. Hence, there is no
realistic way to define this correlation in our analysis.
Our analysis constitutes, to our knowledge, one
of the largest series of solid tumors tested for MDM2
amplification at a single center. We do recognize that it
is not without its limitations. For instance, our study was
a retrospective analysis and is hence prone to selection
bias. We were also restricted to disclose the identity of
the MDM2 inhibitors used in our analysis. We could
not validate positive MDM2 amplification results using
fluorescence in situ hybridization or immunohistochemical
analysis. Because MDM2 amplification was analyzed in
multiple tumor types, the number of cases with MDM2
amplification per tumor type is small for any meaningful
analysis of correlations. Some gene alterations that cooccurred with MDM2 amplification in our analysis did not
meet statistical significance and the probability that these
represent chance events cannot be excluded. We refrained
from making comparisons between our analysis and the
TCGA dataset since it would not have been accurate—as
mentioned earlier, the TCGA dataset is mainly comprised
of samples from patients in the earlier stages of cancer,
whereas our patient population in consisted mainly of
metastatic, recurrent and pre-treated patients. Regardless
of these limitations, we found that MDM2 amplification in
solid tumors was associated with liposarcoma, metastatic
breast cancer, CDK4 amplification, TP53 mutation,
CDKN2A/B loss, and MYC amplification.
Our finding that MDM2 and CDK4 amplification
were often co-expressed suggests that therapeutic
strategies combining MDM2 and CDK4 inhibitors might
have promise in patients whose tumors express both of
these aberrations. Further studies are necessary to better
identify and treat these patients. Moreover, our results also
emphasize the importance of assessing the TP53 mutation
status in all patients found to have MDM2 amplification.
had been histologically confirmed by the Department of
Pathology at MD Anderson. Data were collected from
transcribed notes and radiology reports in the electronic
medical record and other sources of documentation. All
patients had been registered in the institutional patient
database, and all clinical, pathologic, and laboratory
assessments had been performed at the institution. The
study and all treatments were conducted according to
the guidelines and with the approval of the Institutional
Review Board.
MATERIALS AND METHODS
Treatment and evaluation
Tissue samples and molecular analysis
We analyzed 523 clinical cases with various disease
origins using comprehensive genomic profiling in a
Clinical Laboratory Improvement Amendments-certified,
College of American Pathologists-accredited laboratory
(Foundation Medicine, Cambridge, MA, USA). The
pathologic diagnosis of each case was confirmed by
routine hematoxylin and eosin staining, and all samples
forwarded for DNA or RNA extraction contained a
minimum of 20% tumor nuclei. Extensive technical
descriptions and validation of the genomic profiling
assays used to analyze these samples in the course of
clinical care have been published previously [48, 49].
In summary, 50 nano grams of DNA was extracted
from 40 microns (10 x 4 microns) thick cuts of tumor
sample from formalin-fixed, paraffin-embedded tissue
blocks or slides. Targeted next-generation sequencing
was performed on hybridization-captured, adaptor
ligation-based libraries for all coding exons of at least
236 cancer-related genes, including MDM2 gene, plus
select introns from at least 19 genes that are frequently
rearranged in cancer. For those samples for which RNA
was available, targeted RNA sequencing was performed
for enhanced rearrangement analysis in 265 genes [49].
Sequencing of captured libraries was performed using
the Illumina HiSeq 2000 or HiSeq 2500 platforms to a
mean exon coverage depth of 1164X, and the resultant
sequences were analyzed for base substitutions,
insertions, deletions, copy numbers (CNs) alterations
(focal amplifications and homozygous deletions), and
select gene fusions.
Six patients in the study cohort were enrolled
in a phase I clinical trial involving MDM2 inhibitor.
This enrollment occurred at the discretion of treating
physicians and per the availability of an appropriate
clinical trial. Treatment was continued until the onset of
disease progression or unacceptable toxicity, according
to the specific treatment protocol for each trial. Clinical
assessments were performed as specified in each
protocol, typically before the initiation of therapy and
then at the beginning of each new treatment cycle.
Patients
We retrospectively reviewed the electronic medical
records of patients with solid tumors who were referred
to the Department of Investigational Cancer Therapeutics
at The University of Texas MD Anderson Cancer Center,
Houston, Texas from January 2011 through January
2016 and for whom results of a clinical next-generation
sequencing-based assay (Foundation One) were available.
Patients were eligible for inclusion if their malignancy
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Response was assessed from computed tomography
scans at baseline before treatment initiation and then
every 2 cycles during the first 6-8 cycles. All images
were read in the Department of Radiology and were
reviewed by the Department of Investigational Cancer
Therapeutics tumor measurement clinic. Responses
were categorized according to RECIST 1.1 (Response
Evaluation Criteria in Solid Tumors) criteria on the basis
of specific protocol requirements and were reported as
the best response [50, 51]. We also calculated the Royal
Marsden Hospital (RMH) score, which is a prognostic
score based on 3 survival-associated objective markers
(serum albumin level, serum lactate dehydrogenase level,
and number of metastasis sites). The RMH score was
developed in 2009 to improve patient selection for phase
I clinical trials [20].
ACKNOWLEDGMENTS
We thank the patients and their families for enrolling
in clinical trials. The authors would like to sincerely
thank Kathrina Marcelo-Lewis, PhD of the Department
of Investigational Cancer Therapeutics at The University
of Texas: MD Anderson Cancer Center for assisting in
the editing of this manuscript, and the Department of
Scientific Publications at The University of Texas MD
Anderson Cancer Center, Houston, Texas for their help in
reviewing this manuscript.
CONFLICTS OF INTEREST
The following authors declare no potential conflicts
of interest: Dr. Dembla, Dr. Barata, Dr. Hess, Dr. Fu, Dr.
Karp, Dr. Subbiah, and Dr. Shaw.
Dr. Naing has received research funding from NCI,
EMD Serono, Medimmune, Healios Oncology Nutrition,
ATTEROCOR, Amplimmune, ARMO Biosciences,
Karyopharm Therapeutics, Incyte, Novartis, Regeneron,
and Baxter (spouse).
Dr. Somaiah has a consulting or advisory role with
Bayer.
Dr. Piha-Paul’s funding sources include Genentech,
GlaxoSmithKline, Puma Biotechnology, Inc., Novartis,
Merck Sharp and Dohme, Medivation, Inc., Principia
Biopharma, Inc., AbbVie, XuanZhu Biopharma, Helix
BioPharma Corp., Incyte, Inc., Hoffman LaRoche, Curis,
and Cerulean. She has received an honorarium from
Genentech.
Dr. Janku has research funding from Novartis,
Astellas, Agios, BioMed Valley Discoveries, Array, Roche,
Plexxikon, Deciphera, Trovagene, and Biocartis. He has a
consulting or advisory role with Sequenom, Trovagene,
Deciphera, Novartis, and Foundation One.
Dr. Tsimberidou has received funding from
Foundation Medicine, Merck Serono, Onyx, Baxalta, and
Bayer.
Dr. Meric-Bernstam has received grant and research
support from Novartis and Aileron.
Dr. Hong has stock or other ownership in
Oncoresponse and Molecular Match. He has received
honoraria from Adaptimmune, Baxter, Bayer, and
Merrimack. He has a consulting or advisory role with
Baxter and Bayer. He has received research funding
from Bayer, Lilly, Genentech, LOXO, Pfizer, Amgen,
Mirati, Ignyta, Merck, Daichi-Sanka, and Eisai. His travel
accommodations or other expenses have been paid or
reimbursed from LOXO and MiRNA. He is the founder
of Oncoresponse.
Statistical analysis
Cox proportional hazards regression analysis was
used to estimate hazard ratios along with corresponding
confidence intervals and p-values. Survival curves were
estimated using the Kaplan–Meier method. Median
survival time was estimated as the point at which the
survival curve crossed 50%. The proportions between
groups were compared by chi-squared tests or Fisher exact
tests, as appropriate for the data.
Patient characteristics, including demographics,
tumor type, tumor MDM2 amplification status, and
associated genetic abnormalities, were summarized by
descriptive statistics. All statistical analyses were carried
out using S+ 8.2 for Windows (TIBCO Software, Inc.,
Palo Alto, CA, USA).
Abbreviations
OS: Overall Survival; ECOG: Eastern Cooperative
Oncology Group; NOS: not otherwise specified; NA: not
applicable. RMH: Royal Marsden Hospital score; CUP:
carcinoma of unknown primary.
Author contributions
VD and DSH: Conceived and designed the
manuscript.
VD: Collected, analyzed the data, and wrote the
manuscript.
PB: Helped in writing the manuscript.
KH: Provided statistical analysis, produced the
figures and edited the manuscript.
DSH and KS: Coordinated the research.
NS, SF, FJ, DDK, AN, SAP, VS, AMT, FM, DSH:
Enrolled patients on the trials and followed the patients
on trials.
All authors: Revised, edited the manuscript,
provided critical input, comments and approved the final
version.
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FUNDING
This work was supported in part by Cancer
Prevention Research Institute of Texas Grant RP110584
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12. Onel K, Cordon-Cardo C. MDM2 and prognosis. Mol
Cancer Res. 2004; 2:1-8.
and National Center for Advancing Translational
Sciences Grant UL1 TR000371 (Center for Clinical and
Translational Sciences). The funding sources had no
input into the design and conduct of the study; collection,
management, analysis, and interpretation of the data;
preparation, review, or approval of the manuscript; and
decision to submit the manuscript for publication.
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swings both ways as an oncogene and a tumor suppressor.
Genes Dev. 2010; 24:1580-9. https://doi.org/10.1101/
gad.1941710.
14. Rayburn E, Zhang R, He J, Wang H. MDM2 and human
malignancies: expression, clinical pathology, prognostic
markers, and implications for chemotherapy. Curr Cancer
Drug Targets. 2005; 5:27-41.
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