Pasireotide (SOM230) is effective for
the treatment of pancreatic
neuroendocrine tumors (PNETs)
in a multiple endocrine neoplasia
type 1 (MEN1) conditional knockout
Thomas J. Quinn, BS,aZiqiang Yuan, MD,aAsha Adem, BS,aRula Geha, MD,a
Chakravarthy Vrikshajanani, MD,aWade Koba, BS,bEugene Fine, MD,bDavid T. Hughes, MD,a
Herbert A. Schmid, PhD,cand Steven K. Libutti, MD,aNew York, NY, and Basel, Switzerland
Background. Pasireotide (SOM230), a long-acting somatostatin analogue (LAR), has improved agonist
activity at somatostatin receptors. We tested the effect of SOM230 on insulin secretion, serum glucose
concentrations, tumor growth, and survival using an MEN1 transgenic mouse model.
Methods. Eight 12-month-old conditional Men1 knockout mice with insulinoma were assessed. The
treatment (n = 4) and control groups (n = 4) received monthly subcutaneous injections of SOM230 or
PBS. Serum insulin and glucose levels were determined by enzyme-linked immunosorbent assay and
enzymatic colorimetric assay, respectively. Tumor activity, growth, and apoptosis were determined by
microPET/CT scan and histologic analysis.
Results. On day 7, there was a decrease in serum insulin levels from 1.06 ± 0.28 mg/L to 0.37 ± 0.17
mg/L (P = .0128) and a significant increase in serum glucose from 4.2 ± 0.45 mmol/L to 7.12 ± 1.06
mmol/L (P = .0075) in the treatment group but no change in the control group. Tumor size was less in
the treatment group (2,098 ± 388 mm2) compared with the control group (7,067 ± 955 mm2;
P = .0024). Furthermore, apoptosis was increased in the treatment group (6.9 ± 1.23%) compared
with the control group (0.29 ± 0.103%; P = .002).
Conclusion. SOM230 demonstrates antisecretory, antiproliferative, and proapoptotic activity in our
MEN1 model of insulinoma. Further studies of the effects of SOM230 in PNET patients with MEN1
mutations are warranted. (Surgery 2012;152:1068-77.)
From the Department of Surgery,aClinical Nuclear Medicine,bAlbert Einstein College of Medicine,
New York, NY; and Novartis Pharmaceuticals,cBasel, Switzerland
THE INCIDENCE OF PANCREATIC NEUROENDOCRINE TUMORS
(PNETs) in the general population is between 1.4%
and 3.1%.1This may be an underestimate because
may or may not produce symptoms, and autopsy re-
ports demonstrate an incidence as great as 10%.2
A retrospective epidemiologic study of neuroendo-
crine neoplasms using the SEER database demon-
strated a 5-fold increase in the annual age-adjusted
incidence rate between the years 1973 and 2004.3
Within the neuroendocrine tumors, PNETs have an
annual age-adjusted incidence rate of 0.32/100,000
from 2000 to 2004 with a median survival of 136
months for localized PNETs, 77 months for
regional PNETs, and 24 months for metastatic
PNETs.3PNETs can be classified by hormonal pro-
duction, with insulinomas being the most common
(17%), followed by gastrinomas (15%), VIPomas
(2%), and glucagonomas (1%); the remaining 65%
have no detectable hormonal production.4
This work was supported in part through a generous gift from
Linda and Earle Altman.
Accepted for publication August 16, 2012.
Reprint requests: Steven K. Libutti, MD, FACS, Director,
Montefiore-Einstein Center for Cancer Care, The Marvin L.
Gliedman, M.D. Distinguished Surgeon, Professor and Vice-
Chairman, Department of Surgery, Professor, Department of
Genetics, Montefiore Medical Center/Albert Einstein College
of Medicine, Greene Medical Arts Pavilion 4th Floor, 3400
0039-6060/$ - see front matter
? 2012 Mosby, Inc. All rights reserved.
The treatment of insulinomas can be divided into
two complementary therapeutic paradigms: surgical
therapy and/or medical therapy. Surgical therapy is
neoplasm can be precisely pin-pointed (via modali-
ties suchas: helical
endoscopic ultrasonography, laparoscopic ultraso-
nography [intraoperative], as well as calcium stimu-
lated arteriography), enucleated or excised, and
metastases can likewise be resected. If metastases
develop or surgical resection is incomplete, medical
therapy is used to diminish symptoms. Patients with
unresectable metastases are educated to prevent
episodes of hypoglycemia by avoiding extended
periods of fasting by encouraging frequent snack-
ing.5In conjunction with dietary modification, spe-
cific medical therapy is initiated to mitigate the
symptoms of metastatic disease.
Diazoxide, a benzothiadiazine derivative, is a
medication used commonly to treat insulinomas
because of its hyperglycemic effects, which arise via
its activation of an ATP-sensitive K+channel, result-
ing in hyperpolarization of the b cell, which subse-
quently inactivates a voltage-gated Ca2+channel
that is requisite for insulin release.6Restoration
of normal glucose levels with diazoxide has been
reported to be as low as 59% with side-effects expe-
rienced by 47% of patients, which include: fluid re-
tention, hirsutism, hypotension, and one reported
case of Stevens-Johnson syndrome.7-9Alternatively,
a long-acting somatostatin analogue can be used to
inhibit the release of insulin.
Octreotide, a somatostatin analogue, has the
ability to inhibit somatostatin receptor (sstr) 2 and
sstr5.10To date, there are 5 main sstr subtypes
(sstr1-5) described in human physiology, with sstr2
and sstr5 expressed in approximately 70% of insu-
linomas; however, 30% of insulinomas express
some other sstr subtype, which is of particular clin-
ical relevance.11For instance, if the insulinoma ex-
presses sstr2, then the action of octreotide will
tend to inhibit the release of insulin, thus restoring
glucose to optimal levels. In contrast, if the insuli-
noma lacks sstr2, octreotide can exacerbate hypo-
glycemia via its inhibition of glucagon and
growth hormone secretion.10Consequently, it is
important to discover alternative treatments that
lack the uncertainty of diazoxide and octreotide
and may be more effective in the treatment of
PNETs. To that end, a novel long-acting release so-
matostatin analogue, pasireotide (SOM230), has
been developed that demonstrates improved ago-
nist activity at multiple sstr subtypes.
SOM230 (Novartis) is a cyclohexapeptide soma-
tostatin analogue with improved agonist activity at
sstr1, 2, 3, and 5 with the greatest activity at sstr5,
2, 3, and 1, respectively.12,13In preclinical studies,
SOM230 decreases tumor volumes in prolacti-
nomas and decreases the secretion of growth
hormone and insulin-like growth factor.14-16Con-
sequently, we sought to investigate the effects of
SOM230 on the secretion of insulin as well as its
effect on tumor volume and survival in a mouse
model of insulinoma.
Loss of heterozygosity of the MEN1 gene leads
to the multiple endocrine
1 (MEN1) syndrome seen in humans, which is
characterized by anterior pituitary adenoma, par-
athyroid hyperplasia, and enteropancreatic endo-
crine tumors.17In addition, mutations in the
MEN1 gene are seen in approximately 44% of
sporadic PNETs.18To recapitulate the human dis-
ease in a mouse model, our laboratory developed
a transgenic mouse line that uses a pancreas-
specific promoter, Pdx1, in combination with the
Cre-Lox system to conditionally knockout Men1
in the pancreata of mice (Pdx1-Cre:Men1 floxed/
floxed). As discussed at length elsewhere, this
mouse model leads to the selective development
of a single insulinoma.19Consequently, with the
development of an insulinoma in our mouse
model, a parallel of one phenotypic expression
seen in MEN1, we sought to investigate the effects
of SOM230 on insulin and glucose levels, apopto-
sis, tumor size, and overall survival.
Animals. Eight 12-month-old mice carrying the
Men1 allele flanked by loxP sites with Cre recombi-
nase under the promoter of the pancreas-specific
transcription factor Pdx1 (Pdx1-Cre:Men1 floxed/
floxed) were used in this study. Moreover, as dem-
onstrated by our laboratory previously, these mice
develop an insulinoma as evidenced by increased
serum levels of insulin and by microPET/CT ana-
lysi.19All animal experiments were conducted after
approval by the animal care committee of the
Albert Einstein College of Medicine.
Administration of SOM230 and PBS. Mice were
anesthetized with halothane and then shaved on
their flank for subcutaneous injection of either
phosphate-buffered saline (PBS) buffer or SOM230
at a concentration of 160 mg/kg/month (64 mg/
mL) every month for 4 months.
Glucose and insulin levels. The mice under-
went a 24-hour fast before we collected whole
blood via a weekly retro-orbital bleeding tech-
nique at pre- and post-treatments. Serum glucose
was measured by enzymatic colorimetric assay by
the use of a GM7 Analyzer (Analox Instruments,
Volume 152, Number 6
Quinn et al 1069
Lundeburg, MA). Serum insulin was measured by
with the UltrasensitiveMouse Insulin ELISA kit
(Mercodia, Inc) according to the manufacturer’s
Survival and toxicity. Mice were weighed every
week for 4 months as an indicator of toxicity. If
death occurred, the pancreas was collected and
fixed for further analysis.
puted tomography (CT). All mice were imaged
after 3 hours of fasting while breathing 1.5%
isoflurane-oxygen mixture anesthesia to continue
through the imaging procedure. A heating pad
before and during scanning maintained normal
body temperature. A total of 300–400 uCi (12–15
MBq) in 0.1 mL of normal saline [18F] fluoro-2-
deoxyglucose was administered intravenously via
tail vein followed immediately by CT (80 kV, 0.5
mA x-ray gun) on an Inveon Multimodality scan-
ner (Siemens). Subsequent PET imaging was per-
formed (approximately 1 hour after the [18F]
fluoro-2-deoxyglucose injection) by transferring
the mouse on the gantry into the PET device.
List mode data acquisition was corrected for dead-
time counting losses, random coincidences, and
the measured nonuniformity of detector response
(i.e., normalized) but not for attenuation or scat-
ter. After both acquisitions, CT images were core-
gistered with PET images using a previously
stored, linear transformation matrix.
SUV analysis for tumor activity. Analysis was
performed with either ASIPRO or IRW (both Sie-
mens) dedicated software. All image studies are
displayed visually in a rotating, 3D projection to
examine for interpretability and artifact. Manual
regions of interest were defined around pathologic
areas of uptake and compared with coregistered CT
images. Successive scrolling through 2 dimensional
slices (each 1.2 mm thick in the axial images)
volumes. The activity concentration within this
volume divided by the activity per gram of body
mass of total injected radioactivity determines the
standardized-uptake value (SUV). The SUVmax is
the maximum SUV value withineachtumor volume.
SUVmax has been validated in numerous animal
and human models as a reproducible and robust
measure of radioactivity in longitudinal studies.
Furthermore, the glucose levels inour mouse model
did not impact the SUV calculation.
Hematoxylin and eosin staining. Mice were sac-
rificed after 4 months, and whole pancreata were
dissected, formalin-fixed with paraffin embedding,
Fig 1. Evaluation of somatostatin receptor subtypes (sstr1-5) in representative insulinomas from Pdx1-Cre:Men1 floxed/
floxed conditional knockout mice by immunofluorescence. Islets of Langerhans were visualized with anti-insulin anti-
body and corresponding secondary antibody (red), and sstr1-5were identified with anti-sstr1, -sstr2, -sstr3, -sstr4, or
-sstr5 antibodies along with corresponding secondary antibodies (green). All 5 sstr were identified in this mouse model.
1070 Quinn et al
and sectioned (5 mm) on a rotating microtome
(Microm, Walldorf, Germany). Hematoxylin and
eosin staining was performed according to standard
procedures. For morphometric analysis, three
100-mm sections were digitalized, and the pancreas
cross-sectional area in the section with maximal
tumor diameter was determined by computerized
Apoptosis analysis. Apoptotic status in endo-
crine tumor tissues was measured in control and
treated mice by the Terminal deoxynucleotidyl
transferase dUTP Nick End-Labeling (TUNEL)
assay. For quantification of apoptosis, the TUNEL
assay was performed according to the manufac-
turer on paraffin-embedded sections with an In
Situ Cell Death Detection Kit (Roche Diagnostic).
The tissue sections were deparaffinized and trea-
ted with proteinase K (10 mg/mL) for 20 minutes.
The sections were then washed twice with PBS, la-
beled, and stained with the TUNEL reaction mix-
ture (label plus enzyme solutions) for 60 min at
378C, and washed twice with PBS in the dark.
The slides were mounted in Vectashield mounting
medium with DAPI (Vector Laboratories, Burlin-
game, CA). The apoptotic fluorescent cells were
counted under a fluorescent microscope, and the
numbers were expressed as the percentage of total
cells ± SD. A negative control without enzyme treat-
ment and a positive control with DNase I treat-
ment also were performed.
SSTR detection. The detection of sstr1-5 in
pancreatic endocrine tumor tissue was measured
in our mouse model. Immunofluorescent staining
(Abs; BD Biosciences) and were incubated at a 1:50
dilution overnight at 48C, respectively. Pig anti-
insulin Ab was also used for identification of b cells.
Sections were then washed with PBS and were
incubated with a 1:200 dilution of anti-rabbit or
anti-goat Alexa Fluor 488 and anti-pig Alexa Fluor
respectively. A negative control without primary
antibody was also performed.
Fig 2. Effect of pasireotide (SOM230) on serum insulin (A) and glucose levels (B) in Pdx1-Cre:Men1 floxed/floxed con-
ditional knockout mice with monthly subcutaneous injections of SOM230 (160 mg/Kg/month [64 mg/ml]) or PBS for
four months (mean ± SD). *One-way repeated ANOVA was performed on data as long as there were at least 3 mice in
each group (ie, up to and including day 70). yIndicates the occurrence of death (days 68, 74, and 82).
Volume 152, Number 6
Quinn et al 1071
Statistical analysis. Statistical analysis was per-
formed using GraphPad Prism v.5.0a in conjunc-
tion with Microsoft Excel 2010. An unpaired t test
with a Welch correction for nonequal variance was
used for image data quantification, and a one-way
repeated ANOVA was used to analyze serum
insulin levels and serum glucose levels.
Pdx1-Cre;Men1 floxed/floxed conditional knock-
out mice express somatostatin receptor subtypes
1–5 (sstr1-5) (Fig 1). For SOM230 to be a feasible
treatment in our Pdx1-Cre;Men1 floxed/floxed condi-
tional knockout mouse model, we first had to iden-
tify the presence of sstrs. Our results demonstrated
that sstr1-5 were expressed in the PNET tissues of
the mouse model used in this study. The presence
of sstr1-5 in the PNETs of our mouse model
supports the proposed mechanism of action of
SOM230, namely, its activity as a somatostatin
Subcutaneous (SC) injection of SOM230 de-
creases serum insulin levels and increases serum
glucose levels in Pdx1-Cre; Men1 floxed/floxed condi-
tional knockout mice (Fig 2). To study the antise-
cretory effects of SOM230, baseline serum insulin
levels in the control and treatment groups were
measured with no significant difference between
the 2 groups: 1.08 ± 0.13 mg/L and 1.06 ± 0.28
mg/L, respectively (P = .9096). By day 7 after ad-
ministration of PBS or SOM230, there was a differ-
ence in serum insulin levels between the control
and treatment groups: 1.43 ± 0.19 mg/L and 0.37
± 0.17 mg/L, respectively (P = .0004). Furthermore,
with monthly SC injections, the ability of SOM230
to decrease insulin levels, compared with SC PBS
injections, remained significant over the four
months of treatment (P <.0001). The baseline se-
rum glucose levels measured in the control and
treatment groups, before treatment initiation,
were not different: 4.29 ± 0.31 mmol/L and
4.25 ± 0.45 mmol/L , respectively (P = .88). In
Fig 3. microPET/CT and SUV analysis as a means of visualizing insulinoma responsiveness to monthly subcutaneous
injections of pasireotide (SOM230; 160 mg/kg/month [64 mg/mL]) or PBS over 4 months. (A) microPET/CT
demonstrating the presence of increased metabolism/excretion by normal organs (brain, heart, kidneys, and blad-
der) and an insulinoma before treatment with SOM230 (arrow). (B) microPET/CT demonstrating increased metab-
olism/excretion by normal organs with decreased activity in the insulinoma after 4 months treatment with SOM230.
(C) SUV measurements for each mouse represented as a percent change in activity beginning from pre-treatment
until either death or four months treatment with either SOM230 or PBS (100 3 [SUVfinal? SUVpre-treatment]/
SUVpre-treatment). Mice M2, M3, and M4 of the PBS group expired before completion of the study (days 68, 74,
and 82, respectively).
1072 Quinn et al
contrast, 7 days after SC injection of SOM230, se-
rum glucose levels in the treatment group were
greater than those in the control group: 7.12 ±
1.06 mmol/L and 4.21 ± 0.35 mmol/L, respectively
(P = .0136). The increase in serum glucose levels
was sustained during the 4-month experiment in
the group receiving monthly SC injections of
SOM230 as compared with monthly PBS injections
(P < .0001).
SC injection of SOM230 demonstrated a de-
crease in tumor activity on PET/CT in Pdx1-Cre;
(Fig 3). During the 4-month study period, 2 of
the 4 mice in the treatment group had a decrease
in SUV compared with baseline by as much as 68%.
The remaining 2 mice had an increase of 44% and
17%. In contrast, the only control mouse to survive
the study had an increase in tumor activity of
124%. Of the 3 control mice that did not survive
(death on days 68, 74, and 82), the increase in tu-
mor activity was 3%, 17%, and 125%, respectively.
Of note, the 2 control mice that died early in the
study had a minimal change in tumor activity be-
cause of the fact that they did not survive long
enough for a change to be observed. In contrast,
the other 2 control mice survived long enough
for the serial microPET/CT to identify a change
in tumor activity, approximately 3- to 7-fold of
that seen in the 2 mice in the treatment group
with increased tumor activity. This observation sug-
gests that SOM230 may also decrease tumor activity
via an antiproliferative and/or proapoptotic mech-
anism. In contrast, none of the mice in the control
group had a reduction in SUV compared with
SC injection of SOM230 decreased PNET size
in Pdx1-Cre; Men1 floxed/floxed conditional knock-
out mice compared to PBS treated mice (Fig 4).
At the completion of the study, all remaining
mice were sacrificed by CO2inhalation. Pancreata
from all mice (including those that died during
the study) were collected, sectioned (3 sections/
mouse), and prepared for microscopic analysis by
hematoxylin and eosin (H&E) staining to identify
the size of the insulinoma from each mouse. The
control group had a greater mean tumor (7,067
± 955 mm2vs. 2,098 ± 388 mm2, P = .0024) size, as
seen at the same magnification of 2.5x. The
Fig 4. Histologic analysis of pancreata from Pdx1-Cre:Men1 floxed/floxed conditional knockout mice with monthly SC in-
jections of PBS or pasireotide (SOM230) (160 mg/kg/month [64 mg/mL]) for four months at same magnification
demonstrating a difference in tumor size. (A) Hematoxylin and eosin staining of representative pancreas with insuli-
noma from the control group receiving monthly SC injections of PBS at the end of 4 months at 2.5x magnification.
(B) Hematoxylin and eosin staining of representative pancreas with insulinoma from the treatment group receiving
monthly SC injections of SOM230 at the end of 4 months at 2.5x magnification. (C) Mean insulinoma size in control
and treatment group after 4 months.
Volume 152, Number 6
Quinn et al 1073
decrease in measured tumor size between the
two groups is consistent with the results of the mi-
croPET scans and SUV calculations.
SC injection of SOM230 increases apoptosis in
PNETs in Pdx1-Cre; Men1 floxed/floxed conditional
knockout mice (Fig 5). Sections of pancreata (3 sec-
tions/mouse) from the treatment and control
groups were evaluated for the presence of apopto-
tic cells via a TUNEL assay. The proportion of ap-
optotic PNET cells in the control groups was less
than in the treatment group (0.299 ± 0.103% vs.
6.92 ± 1.23%; P = .002).
SC injection of SOM230 improved survival in
Pdx1-Cre; Men1 floxed/floxed conditional knockout
mice. Within the treatment group (n = 4), there
was no mortality, and all mice were alive at the
end of the 4-month study period; however, in the
control group, only 1 of the 4 mice was alive at
the conclusion of the experiment, with the cause
of death believed to be associated with metabolic
dysfunction caused by chronic hypoglycemia.
Although operative resection remains the pri-
mary treatment of PNETs, it is important to con-
sider those patients not amenable to resection
because of the presence of unresectable primary or
metastatic lesions. Indeed, medical therapy devel-
oped during the past 60 years can ameliorate the
symptoms produced by functional PNETs such as
insulinomas. However, even with the use of benzo-
thiadiazine derivatives, such as diazoxide, and
narrow-spectrum somatostatin analogues, such as
octreotide, there remains a group of individuals
whose symptoms are not alleviated by these med-
ications. The aim of this study was to determine
whether a long-acting release somatostatin ana-
logue, pasireotide (SOM230), with broadened sstr
subtype activity can be an effective antisecretory,
antiproliferative, and proapoptotic therapy in a
mouse model of insulinoma.
This Pdx1-Cre: Men1 floxed/floxed mouse model
of insulinoma recapitulates the human phenotype
Fig 5. Assessment of apoptosis in representative pancreata from Pdx1-Cre:Men1 floxed/floxed conditional knockout
mice after monthly SC injections of PBS or pasireotide (SOM230) (160 mg/kg/month [64 mg/mL]) for 4 months
by TUNEL assay. (A) Immunofluorescent staining of representative pancreas with insulinoma from the control
group receiving monthly SC injections of PBS at the end of 4 months. Nuclei were visualized via DAPI staining
(blue), whereas apoptotic foci were identified by terminal deoxynucleotidyl transferase-mediated addition of
fluorescein-dUTP (green). (B) Immunofluorescent staining of representative pancreas with insulinoma from the
treatment group receiving monthly SC injections of SOM230 at the end of 4 months. (C) Quantification was
achieved by counting the apoptotic fluorescent cells under a fluorescent microscope (expressed as the percentage
of total cells ± SD).
1074 Quinn et al
as evidenced by the markedly increased basal insu-
lin levels measured by ELISA in mice before treat-
ment. Furthermore, the increased insulin levels
led to markedly decreased serum glucose concen-
trations, a finding consistent with the pathophysi-
ologyof human insulinomas.
microPET/CT allowed quantification of the meta-
bolic activity of PNET as well as localization of
the insulinoma in the pancreas of the mouse
model. Finally, histology of the collected pancreata
demonstrated an expansion of the islet of Langer-
hans, as visualized with hematoxylin and eosin
staining, and immunofluorescence confirmed in-
sulin secretion as well as characterizing the sstr
subtypes found in the PNETs of this mouse model.
Monthly SC injections of SOM230 led to
a sustained decrease in serum insulin levels,
a finding that is consistent with both the mecha-
nism of action of somatostatin analogues as well
as the specific binding affinity of SOM230 for
sstr1, 2, 3, 5. Importantly, the half maximal
inhibitory concentration (IC50) of SOM230 for
sstr5 and sstr2 is reported to be 0.1 nM and 1.0
nM, respectively, whereas the IC50of octreotide
for sstr5 and sstr2 is reported to be 7 nM and
0.6 nM, respectively.13This measurement is of
particular clinical relevance, as approximately
70% of human insulinomas are estimated to ex-
press sstr5 or sstr211and these are the main sstr
subtypes that when activated are associated with
a decrease in hormone secretion, with sstr2 being
the primary receptor involved.20Moreover, an
mRNA expression study concluded that there is
an association of sstr5 with insulinoma aggressive-
ness, an expression profile which tends to be less
responsive to octreotide administration.21
such, this study is the first to investigate the use
of a somatostatin analog with enhanced sstr5 ac-
tivity without compromising sstr2 activity to re-
store serum insulin to physiologically compatible
levels and may be useful for the treatment of ma-
In addition to the antisecretory effects of soma-
tostatin analogues, primarily through interaction
with sstr2, an antiproliferative effect has been
associated with activity of both sstr5 and sstr2.20
A recent study of the effects of SOM230 on pitui-
tary adenomas demonstrated a decrease in tumor
volume compared to treatment with octreotide,
a finding consistent with the sstr binding spectrum
of SOM230.14To that end, our study also demon-
strated a decrease in tumor volume in the
treatment group compared to the control group
as measured by morphometric analysis with stan-
dard hematoxylin and eosin staining as well as by
The use of
microPET/CTanalysis, using SUV values measured
before and after treatment acquired monthly.
Furthermore, the various sstr subtypes are not
limited to antisecretory and antiproliferative ef-
fects but alsoinclude
A recent study demonstrated that SOM230 has
a proapoptotic effect on hyperplastic cells in the
rat mammary gland, mediated through sstr3.22
Analogously, our study demonstrated an increase
in apoptotic events as evidenced by a TUNEL as-
say, with increased DNA fragmentation in the
pancreata of mice treated with SOM230 vs. the
pancreata of mice treated with PBS. This finding
SOM230 may not only alleviate symptoms in pa-
tients with insulinomas but might also lead to re-
gression of the tumors.
Finally, an overall increased survival in the
treatment group compared to the control group
was observed at the end of this study. Although
statistical analysis was obviated because of the small
sample size, the overall magnitude of increased
survival in the treatment group (100%) compared
to the control group (25%) is extremely suggestive
of an effect and warrants further investigation.
We thank Novartis Pharmaceuticals for providing
SOM230 for this study.
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Dr Menno Vriens (Utrect, Netherlands): I have a ques-
tion about the timeline. Could you explain a little
more about if you had a minimal size of the tumor be-
fore you started to give the SOM230, and, if so, if there
was a dose depending on the relationship between
growth and a decrease in proliferation to the tumor.
Mr Thomas Quinn: We used a dose that was selected
by Novartis on the basis of their experiments in rat
models; therefore, we used a given concentration that
was already provided to us. We didn’t really look at
a dose-dependent response but rather, what was the ac-
cepted nontoxic dose in this mouse model.
And so that’s what we had used. And we didn’t
actually look at whether or not there was a dose-
Dr Menno Vriens (Utrect, Netherlands): I was won-
dering at what time you started with the SOM230 and
if you had a minimal size of your tumor.
Mr Thomas Quinn: We initiated the treatment when
the mice were 12 months old. This mouse model had
been previously developed in our laboratory. And that’s
when we have determined the optimal tumor presence,
at 12 months of age in the mice, and that’s when we ini-
tiated the treatment with pasireotide.
Dr Douglas Evans (Milwaukee, WI): The control
mice, did they die of hypoglycemia? What was the cause
of the death in those mice?
Mr Thomas Quinn: We didn’t actually investigate
thoroughly their cause of death at this point. It’s be-
lieved that it was attributable to the hypoglycemia
because these mice don’t actually develop metastatic dis-
ease because they die too quickly. And we presume that
it’s due to the aberrant insulin and the hypoglycemia.
The actual cause of death hasn’t been fully deter-
mined, but we attribute it to the metabolic dysfunction
Dr Douglas Evans (Milwaukee, WI): I may have
missed this, but did you then sacrifice control and study
mice at the same time and look at the size of the tumors
in the pancreas?
Mr Thomas Quinn: In the study, 3 of the control mice
died during the course of the study. We collected their
pancreata and we prepared them for analysis at the
end of the study. And, at the end of the 4 months, we sac-
rificed all of the remaining mice, collected their pancre-
ata, and analyzed their tumors as well.
We took the mean tumor size of every mouse in the
treatment group and in the control group. We compared
the tumors, using 300-mm section slices through the
tumor to get an average tumor size for each mouse.
Dr Douglas Evans (Milwaukee, WI): And so they were
Mr Thomas Quinn: There wasn’t any difference. Be-
cause these mice had died so early, their tumors had ac-
tually progressed to roughly the same size as the tumors
in the PBS mouse that had survived the 4-month
Dr Douglas Evans (Milwaukee, WI): So with your
model, I think the issue of the analog-inhibiting secre-
tion is probably well established. But an oncologic or
Mr Thomas Quinn: Agreed. And we didn’t actually
look at tumor reduction size, because we didn’t have
an initial tumor size. We could only compare the tumor
1076 Quinn et al
size at the end of the study. So we could compare tumor
sizes only at one point, at the end of the study.
Dr Steven Libutti (Bronx, NY): Just one point of
The tumors start out all at approximately similar sizes.
We know this from establishing the model and looking
at the insulinomas at approximately 12 months of age in
the mice. So there is some variability. And, obviously, it’s
difficult to be able to measure the same tumor in the
same mouse over time.
So that’s why we did the PET scanning, to get some
idea at least of tumor activity or metabolic activity. And
so the PET scans demonstrated, for the most part, that
the only mice where we saw actual reduction of activity
were the mice receiving the treatment.
That, together with the induction of apoptosis,
we think demonstrates antitumor activity, although
Dr Evans’s question is an excellent one. We could not
do comparisons in the same mouse of baseline physical
measurement versus physical measurement at the end of
But, on average, when we look at the mice in the
control group versus the mice in the treatment group,
and we took the measurements of those tumors, the
tumors are smaller in the treatment group than they are
in the control group.
Dr Sareh Parangi (Boston, MA): I was wondering, why
that are kind of more in the weeks rather than months
phase and would allow you to study more animals cheaply
with this drug and kind of sacrifice them every few weeks
since they die by 9 or 10 or 12 weeks, rather than months?
What is the benefit of this particular model?
Mr Thomas Quinn: I’m not really familiar with all of
the other insulinoma mouse models, but I do know that
we showed that our mouse model better recaptiulates
the human disease. And so these mice develop specific
insulinomas only in the pancreata. And by doing that,
we were able to selectively look at the response of the in-
sulinomas in the mice to the treatment.
And also, the microenvironment of these tumors is
more compatible with what is seen in human disease.
I’m not too familiar, again, as I said, with the other
mouse models. But that’s why we used it. And also, we
already had these mice in our study because it was
developed in our lab. So we already had access to them.
Dr Steven Libutti (Bronx, NY): I’ll just address that
real quick. The other most common animal model for
insulinomas is the RIP-Tag model. The problem is,
though, the RIP-Tag model bears no actual relationship
to human pancreatic neuroendocrine tumors in terms of
the cause of the insulinomas; that is, expression of large
T-antigen, which is not known to be a driving cause of
human neuroendocrine tumors.
So the reason we developed this model originally was
to have a model that more closely recapitulated a
condition in patients that resulted in insulinomas. And
what helps us a little bit in having confidence that this
model may be useful to us for other studies is the
observation from Hopkins about 18 months ago that
approximately 44% of sporadic pancreatic neuroendo-
crine tumors actually harbor MEN1 mutations.
So we think this will be a useful model for studying
mechanism, natural history, and effective therapies that
might be generalizable to PNETs in the sporadic setting
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