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Vol. 3, 993-998, June 1997 Clinical Cancer Research 993
Telomerase Elevation in Pancreatic Ductal Carcinoma Compared
to
Nonmalignant Pathological States
Nobuhiro Suehara, Kazuhiro Mizumoto,’
Tsuyoshi Muta, Yohei Tominaga, Hideo Shimura,Shigetaka Kitajima,
Naotaka Hamasaki,Masazumi Tsuneyoshi, and Masao TanakaDepartments
of Surgery I [N. S., K. M., Y. T., H. S., M. Ta.], Clinical
Chemistry and Laboratory Medicine [T. M., S. K., N. H.], and
Pathology 2 [M. Ts.], Kyushu University Faculty of
Medicine,Fukuoka 812-82, Japan
ABSTRACT
Telomerase activity was measured in surgically re-
sected tissues of 20 human pancreatic ductal carcinomas, 12
adenomas, 5 pancreatitis tissues, 14 normal pancreatic
ducts, and 13 normal pancreatic tissues (primarily made up
of acinar cells) using a PCR-based telomerase assay. Rela-
tive telomerase activity was expressed as the equivalent
telomerase intensity of the number of cells of a human
pancreatic cancer cell line, MIA PaCa-2, per microgram of
protein in the tissue samples. The median value (25th per-
centile, 75th percentile) of relative telomerase activity
inpancreatic carcinomas was 13.2 (3.58, 244), which was sig-
nificantly higher relative to normal tissues, normal ducts,
pancreatitis tissues, and adenomas (P < 0.0001). When
thecutoff value of relative telomerase activity was set at 1.00
and 3.00, the positivity rates of telomerase activity in
pan-
creatic ductal carcinomas were 100 and 80%, respectively.
Some of the adenoma samples displayed a weak telomerase
ladder. However, when semiquantitatively analyzed, the rel-
ative telomerase activity of all adenoma tissues was less
than1.00 equivalent cells per microgram protein of the tissues,
which was equivalent to the values encountered in normal
ducts. Thus, our results indicate that reactivation of telo-
merase may occur at a late stage of pancreatic ductal car-
cinogenesis. Therefore, telomerase may be a specific marker
for distinguishing pancreatic cancer from pancreatitis and
adenomas.
INTRODUCTION
Telomerase is an enzyme ribonucleoprotein responsible for
cell immortality, and it synthesizes a six-nucleotide
sequence
designated as TTAGGG of telomeric DNA onto the chrorno-
somal ends in germ-line cells and in immortal cells (1, 2).
Received 10/29/96; revised 2/7/97; accepted 2/25/97.The costs of
publication of this article were defrayed in part by thepayment of
page charges. This article must therefore be hereby marked
advertisement in accordance with 1 8 U.S.C. Section 1734 solely
to
indicate this fact.I To whom requests for reprints should be
addressed. Phone: 81-92-641-1 151, Ext. 5442; Fax: 8
1-92-642-5458.
Although germ-line cells expressing telomerase activity
main-
tam telomeric repeats, somatic cells lose telomeres progres-
sively as the cells undergo cell division (3, 4), which may
lead
to cellular senescence due to the repression of telomerase
ac-
tivity (5, 6). Cancer cells appear to attain immortality with
the
reactivation of telomerase (7).
The conventional assay for telomerase activity requires a
large quantity of cells or tissue (8), which in itself is a
limitation
in the investigation of the role of telomerase in
carcinogenesis.
Recently, a highly sensitive PCR-based assay was developed
to
detect telomerase activity in tissue extracts derived from a
very
small number of immortal cells (7). By this method,
telomerase
activity was detected in approximately 85-90% of various
car-
cinoma tissues such as lung cancer (9), colorectal cancer
(10),
hepatocellullar carcinoma (1 1 ), gastric cancer (1 2), and
breast
cancer (13). In addition, in cultured cells, 98 of 100
immortal
cell populations and none of 22 mortal cell populations cx-
pressed telomerase activity (7). Thus, it is apparent that
telo-
merase is repressed in normal somatic cells and tissues but
is
reactivated in most immortal cells and human cancers. The
results of these studies suggest that telomerase may
ultimately
be required to maintain cell proliferation indefinitely.
Therefore,
detection of telomerase activity in clinically available
specimens
may be of value in the diagnosis of malignant tumors.
Pancreatic cancer is one of the most aggressive malignant
tumors and generally has an extremely poor prognosis (14,
15).
Diagnosis of pancreatic cancer in the early stage may
contribute
to drastic improvement of the prognosis. Human pancreatic
ductal carcinomas display variable but consistent genetic
changes, including mutations of K-ras (16, 17), p53 (18),
APC
(19), andpl6 (20). Ifsuch genetic changes can be detected
using
a small number of cells, they can serve as a clinical marker
to
the diagnosis of cancer. K-ras mutations have been detected
in
the pancreatic juice obtained by endoscopic retrograde
pancre-
atography in 55 to 100% of patients with pancreatic cancer
(21-24). However, K-ras mutations are present in
noncancerous
tissues such as ductal hyperplasia (25) and adenoma (26, 27)
and, therefore, are of limited value as a clue to the diagnosis
of
pancreatic cancer.
We reported previously that telomerase is highly activated
in human pancreatic ductal carcinoma when investigated by a
semiquantitative modified PCR-based assay (28). Apparently,
telomerase is a new prevalent marker for human pancreatic
ductal carcinoma. However, it is not known at which step of
pancreatic carcinogenesis telornerase is reactivated. If
telomer-
ase is activated exclusively in cancer and repressed in
preneo-
plastic lesions of pancreatitis or adenoma, telomerase could
well
be a specific marker of pancreatic cancer. In the present
study,
relative values of telomerase activity were measured in
surgi-
cally resected tissues of pancreatic carcinoma, adenoma,
pan-
creatitis, normal pancreatic ducts, and normal pancreatic
tissues
to evaluate the putative role of telomerase in the diagnosis
of
pancreatic cancer.
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994 Telomerase Elevation in Pancreatic Ductal Carcinoma
Table I Relative values of telo merase a ctivity i n patients w
ith pancreatic aden omas and carcinomas
Case Histology Age Sex” Staging” Differentiation Location Rd
ative tclomerase activity’-Adenomas
25 Serous cystadenoma 82 F Pt 0.44
38 Serous cystadenoma 72 F Pb 0.25
100 Serous cystadenoma 32 M Pt 0.21I 10 Serous cystadenoma 53 F
Pb 0.58
62 Mucinous cystadenoma 54 M Pb-t 0.56
1 15 Mucinous cystadenoma 75 F Pb-t 0.447 Intraductal papillary
adenoma 67 M Ph 0.71
94 Intraductal papillary adenoma 81 F Ph 0.30
102 Intraductal papillary adenoma 46 F Pb-t 0.76
104 Intraductal papillary adenoma 68 F Ph 0.76108 Intraductal
papillary adcnoma 53 F Ph 0.30
I 30 lntraductal papillary adenoma 78 M Pb 0.34
Carcinomas
5 Intraductal papillary adenocarcinoma 72 F TI�,N�M() Ph
2750
35 lntraductal papillary adenocarcinoma 61 F T15NJM() Ph 196
6 Tubular adenocarcinoma 77 M T,N1M1 Well Ph 518,000
59 Tubular adenocarcinoma 72 M T2N,M0 Well Pb 57.5
65 Tubular adenocarcinoma 75 F T3N1M1 Well Ph 5.27
66 Tubular adenocarcinoma 77 F T3N0M#{216} Well Ph 26067 Tubular
adenocarcinoma 59 M T2N1M#{216} Well Ph 3.50
81 Tubular adenocarcinoma 73 M T,N0M0 Well Ph 295
I I I Tubular adenocarcinoma 68 M T3N)M() Well Ph 4.70
I Tubular adenocarcinoma 50 F T3N1M, Moderate Pb-t 8.93
69 Tubular adenocarcinoma 40 M T3N,M0 Moderate Pb-t 2.3576
Tubular adenocarcinoma 69 M T3N0M0 Moderate Ph 1.98
113 Tubular adenocarcinoma 66 F T,N0M0 Moderate Ph 5.19
121 Tubular adenocarcinoma 52 M T1N1MJ Moderate Ph 3.83
131 Tubular adenocarcinoma 53 F T,N0M0 Moderate Ph 2.46
I 2 Tubular adenocarcinoma 55 M T1N0M0 Poor Ph 34.7
83 Tubular adenocarcinoma 59 M T�N)M() Poor Ph 2.17
70 Tubular adenocarcinoma 74 F T,N0M0 Poor Pb-t 970
93 Mucinous cystadenocarcinoma 66 F T3N1M0 Ph 4.98
41 Anaplastic ductal carcinoma 74 F T3N1M0 Pb-t 17.4
,1 M. male; F, female; Ph, head of pancreas: Pb, body of
pancreas; Pt, tail of pancreas; Pb-t, body and tail of
pancreas.
“ Tumor stage is assessed according to UICC-TNM staging (29).‘
Relative values of telomerase activity are expressed as the
equivalent telomerase intensity of the number of cells of MIA
PaCa-2 per microgram
of protein in the tissue samples.
MATERIALS AND METHODSCell Lines and Tissue Samples. The human
pancreatic
cancer cell line MIA PaCa-2, generously provided by Japanese
Cancer Resources Bank (Tokyo, Japan), was cultured in DMEM
(Nissui Pharmaceutical Co., Ltd., Tokyo, Japan) supplemented
with penicillin (1000 units/mI), streptomycin sulfate (100
ji.g/
ml), and 10% heat-inactivated fetal bovine serum.
Tissue samples were obtained at the time of surgery either
at Kyushu University Hospital (Fukuoka, Japan) or at
affiliated
hospitals. Specimens were from 20 primary pancreatic ductal
carcinomas, including 2 intraductal papillary
adenocarcinomas,
16 tubular adenocarcinomas (7 well, 6 moderately, and 3
poorly
differentiated adenocarcinomas), a mucinous cystadenocarci-
noma, and an anaplastic adenocarcinoma; 12 pancreatic adeno-
mas, including 4 serous cystadenomas, 2 mucinous cystadeno-
mas, and 6 intraductal papillary adenomas; 5 pancreatitis
tissues: 14 normal main pancreatic ducts; and 13 normal pan-
creatic tissues (primarily made up of acinar cells). They
were
removed as soon as possible after resection and were stored
at
-80#{176}C until use. Normal pancreatic ducts were taken from
the
main pancreatic duct in patients with pancreatitis and from
the
main ducts apart from the tumor in patients with neoplasms.
Normal pancreatic tissue samples were collected from a
periph-
eral soft part of the pancreas in the same manner. The
tissue
samples in pancreatitis were primarily from a hard portion of
the
pancreatic mass including the stenotic ducts. The samples of
serous cystadenomas or mucinous cystadenomas were obtained
from the cyst wall. In patients with intraductal papillary
adeno-
mas, the affected ducts were opened, and a sample was taken
from a macroscopically distinct tumor. The tissues of
pancreatic
carcinoma were excised from a hard portion of the tumors.
All
tissues adjacent to the specimens were histologically
examined,
and the diagnosis was confirmed. In cases of unresectable
pan-
creatic carcinomas such as were found in patients 12, 69, 93,
and
121 (Table 1), needle biopsies were performed at laparotomy,
and a portion of the same sample was diagnosed
histologically.
The definitions of stage grouping, histological
classification,
and lymphatic metastasis of pancreatic cancers were made ac-
cording to the UICC-TNM2 classification (29).
2 The abbreviation used is: UICC-TNM, International Union
against
Cancer, Tumor-Node-Metastasis.
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Clinical Cancer Research 995
Telomerase Assay. Telomerase activity was measured
as described previously (28). Briefly, the cell pellets from
MIA PaCa-2 were suspended with CHAPS lysis buffer [10 m�i
Tris-HC1 (pH 7.5), 1 mM MgC1.,, 1 m�i EGTA, 0.1 mrvi
4-(2-aminoethyl)-benzenesulfonylfluoride hydrochloride, 5
ms�
�3-mercaptoethanol, 0.5% CHAPS, ]0% glycerol, and protease
inhibitors. The frozen pancreatic tissues were washed once
in
ice-cold PBS and also homogenized with CHAPS lysis buffer in
microtubes with matching pestles. The supernatants (CHAPS
cell extract) were stored at -80#{176}C until use. Protein
concentra-
tion of the tissue extract was measured by Bradford assay
(30),
and 6 or 0.6 �ig extract was used for each telomerase assay.
Telomerase activity was assayed by the modification of the
PCR-based telomerase assay as described by Kim et a!. (7)
and
Tahara et a!. (3 1). The CHAPS cell extracts were incubated
with
reaction buffer containing 50 �1M deoxynucleotide triphos-
phates, 0.3 p.Ci of [a-32P]dCTP. 2 units of Taq DNA polymer-
ase (Promega Corp., Madison, WI), and 0.1 p.g of TS primer
(5’-AATCCGTCGAGCAGAGTF-3’). During this step, 0.1 �g
of CX primer (5’-CCCTTACCCTTACCCTTACCCTAA-3’)
was added, and the reaction mixture was subjected to 3 1 PCR
cycles. Telomerase activity was detected as a 6-base ladder
signal that disappeared with RNase (Boehringer-Manheim
Corp., Manheim, Germany) pretreatment, indicating that the
reaction was specific for telomerase activity (see Fig. 1).
MIA
PaCa-2 extracts equivalent to 1, 10, 102, and ]0� cells were
always measured as a standard per assay, and relative values
of
telomerase activity were expressed as the equivalent
telomerase
intensity of the number of MIA PaCa-2 cells per microgram
protein in each sample as described previously (28). Signal
intensity of the 6-base ladder was measured by NIH image,
version 1 .59 (NTIS, Springfield, VA). A 36-bp internal
standard
(Oncor, Inc., Gaithersburg. MD) was used as an internal
control.
Logarithmic values of the relative telomerase activity were
statistically analyzed by one-way ANOVA and Fisher’s test
because they showed a normal distribution.
RESULTSEfficiency of the PCR reaction was confirmed with the
detection of a 36-bp internal standard (Fig. I). Telomerase
activity in the human pancreatic cancer cell line MIA PaCa-2
was detected as a six-nucleotide repeat ladder, and the
signal
intensity was reduced according to the decrease in the number
of
cancer cells by dilution. Regression analysis was performed
between logarithmic values of the cell numbers and
telomerase
intensity, and the correlation coefficient always exceeded
0.9.
A definite telomerase ladder was not observed in all normal
pancreatic tissue and duct specimens (Fig. la), and the
median
values (25th percentile, 75th percentile) of relative
telomerase
activity expressed by the equivalent telomerase intensity of
the
number of MIA PaCa-2 cells were 0.25 (0.20, 0.45) and 0.31
(0.14, 0.50), respectively. In all pancreatitis sample extracts,
the
telomerase ladder was also undetectable, and the median
value
(25th percentile, 75th percentile) of relative telomerase
activity
was 0. 17 (0.09, 0.46). All relative values of telomerase
activities
of normal pancreas, normal ducts, and pancreatitis were
under
I .00 equivalent cells per microgram of tissue protein.
A telomerase ladder was indistinct in most pancreatic ad-
enomas. However, some of the adenomas presented weak te-
lornerase ladder signals, which would have been regarded as
positive had they been assessed by simple qualitative
telomerase
analysis. Semiquantitatively analyzed, relative telomerase
activ-
ities of each adenoma are listed in Table I . All values of
adenomas were under 1 .00 equivalent cells per microgram of
tissue protein. The median value (25th percentile, 75th
percen-
tile) in adenomas was 0.44 (0.30, 0.68), which was slightly
higher than that encountered in normal tissues and ducts but
not
significantly different from these two groups. Mucinous
cysta-
denomas and intraductal adenomas are generally believed to
have a greater malignant potential than serous cystadenomas.
However, telomerase activity was not significantly different
between these two groups (Table 2).
A telomerase ladder was clearly detected in almost all
pancreatic ductal carcinomas (Fig. la). All of the values of
relative telomerase activity in carcinomas were over 1 .00
equiv-
alent cells per microgram of tissue protein and varied from I
.98
to 518,000. The median value (25th percentile, 75th
percentile)
of relative telomerase activities of ductal carcinomas was
13.2
(3.58, 244), which was significantly higher than that
encoun-
tered in normal tissues, normal ducts, pancreatitis, and
adeno-
mas (P < 0.0001). Relative values of telomerase activity of
all
samples are summarized in Fig. 2 by means of a box-and-
whisker plot analysis, which clearly demonstrates exclusive
activation of telomerase in pancreatic ductal carcinomas.
With
regard to the histological differentiation in pancreatic
ductal
carcinomas, there were no significant differences among
intra-
ductal papillary, well, moderately, and poorly
differentiated
adenocarcinomas. However, relative telomerase activity in
the
group of intraductal papillary and well-differentiated
adenocar-
cinomas was significant when compared to the group of mod-
erately to poorly differentiated adenocarcinomas (Table 2; P
<
0.05). In terms of staging of the disease, the median value
of
telomerase activity in pancreatic ductal carcinomas in the
T1-T2
group tended to be higher than that in the T3-T4 group,
although
the probability value of the difference was 0.0544. There was
no
significant difference between the locations of the
carcinomas,
i.e., pancreatic head versus pancreatic body and tail.
Telomerase activity was measured mixing carcinoma tis-
sues with normal ducts to evaluate the effect of normal cells
on
the telomerase ladder. The intensity of the telomerase ladder
of
carcinoma was reduced to some extent, consistent with the
inclusion of normal ducts (Fig. lb).
DISCUSSION
The present study has revealed that telomerase was defi-
nitely activated in almost all pancreatic ductal carcinomas.
In
addition to the repression of telomerase in normal
pancreatic
tissues, normal ducts that are precursor cells of ductal
carcino-
mas did not show any telomerase ladder. When the cutoff
value
of relative telomerasc activity was set at I .00 and 3.00,
the
positivity rate of pancreatic ductal carcinomas was 100 and
80%, respectively. Furthermore, relative values of
telomerase
activity in pancreatitis or adenomas are comparable to those
of
normal ducts. These results suggest that the possibility
that
telomerase could be a new prevalent marker for pancreatic
ductal carcinoma.
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a
LLg tissue
extractRNase
b
I � I 1 II II
6 6 6 6 6 6 6 6660.6 0.6 0.6
--+--+--+- +- +--
6 6
if
12
996 Telomerase Elevation in Pancreatic Ductal Carcinoma
Internal
(36bp) � � �..control’-#{248}
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Fig. I �i.
telomerase activity signals in pancreatic ductal carcinoma.
adenoma, pancreatitis tissue. normal duct. and normal tissue
samples. From each
tissue sample. an aliquot of the extract containing 6 or 0.6 p.g
of protein with ( + ) or without ( - ) RNase pretreatment was used
in each assay. Aliquotsof the extracts containing I . 10. 102. and
l0� cells of the human pancreatic cancer cell line MIA PaCa-2
having telomerase activity were used as a
standard. Lysis buffer was used as a negative control.
Telomerase activity was detected after electrophoresis of the
enzyme reaction products andautoradiography as a six-nucleotide
repeat ladder. A 36-bp internal standard was used as an internal
control. b: Lane 1. mixing extracts from pancreatic
carcinoma patient 70 (3 �i.g of protein) with 3 p.g of albumin.
Lane 2. mixing extracts from pancreatic carcinoma patient 70 (3 p.g
of protein) withextracts from normal pancreatic duct patient 70 (3
p.g of protein).
Relative values of telomerase activity in pancreatic ductal
carcinomas varied from 1.98 to 518,000. The wide variation
of
the results does not mean instability of the assay per se.
Radio-
activity of �2P is unstable and. as such, difficult to maintain
at
the same level in each analysis. However, determination of
telomerase activity in a human pancreatic cancer cell line
can
standardize the results of each assay. Nearly the same
activity
value was obtained when one sample was analyzed several
times. Pancreatic cancer tissues include variable numbers of
cancer cells along with abundant stromas with fibroblasts,
which
may vary from sample to sample. The study involving mixing
of
carcinoma tissues and normal ducts revealed that normal
cells
could reduce the intensity of the telomerase ladder of
carcino-
mas cells (Fig. lh). In addition to the difference in the
number
of carcinoma cells, the difference in the proportion of
malignant
cells to normal cells in the tissue could be one of the
possible
explanations for the wide variation in the telomerase activity
in
pancreatic ductal carcinomas.
Adenoma-carcinoma sequence can be applied in pancreatic
carcinogenesis as indicated in hamster models of pancreatic
carcinogenesis (32). Clinically, mucinous cystadenoma and
in-
traductal papillary adenoma are presumed to have malignant
potential. Some adenomas showed a clear 6-base ladder, but
the
intensity of the signal was much weaker when compared to any
of pancreatic ductal carcinomas. Recently, it was reported
that
weak telomerase activity was detected in precancerous
lesions,
for example. in 23% of gastric intestinal metaplasias and 50%
of
gastric adenomas (3 1 ). In colorectal lesions, telomerase
activity
was detected in 0% (10) or 100% (31) in adenomas by qualita-
tive analysis. There is still a possibility that weak
telomerase
activity may also be detected in pancreatic adenomas as more
patients with adenoma are evaluated. However, the notable
point is that there is a clear difference in telomerase
activity
expressed between adenomas and carcinomas.
Of practical clinical importance is the distinction between
chronic pancreatitis and pancreatic cancer. It has been
pointed
out that mass-forming pancreatitis masquerades as pancreatic
cancer (33). A preoperative diagnostic tool is sorely needed
to
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10000
1000
100
10
0.1
0.01
Normal Tissues Normal Ducts Pancreatitis Tissues Adenomas
Carcinomas
Clinical Cancer Research 997
Table 2 Relative telomerase activity in patients with normal
pancreatic ducts . adenomas, and carcinomas
Relative tclomcrasc activity” Median
Lesion No. of samples (25th percentile. 75th percentile)
Normal ducts 14 0.31 (0.14, 0.50)
Adenomas 12 0.44 (0.30, 0.68)Scrous cystadenomas 4 0.35 (0.22,
0.55)Mucinous cystadenomas and intraductal papillary adenomas 8
0.50 (0.31. 0.75)
Carcinomas 20 13.2 (3.58. 244)”Differentiation
intraductal papillary and well-differentiated adenocarcinomas 9
196 ( 13.5. 1520)
moderately and poorly differentiated adenocarcinomas 9 3.83
(2.26, 21.8)’
T classification”
T,-1’, 9 196(4.35, 1860)
T3-T4 II 5.27 (2.35. 21.7)
LocationHead 15 5.27 (3.50, 260)Body-tail S 17.5 (5.64. 514)
a Relative values of telomerase activity are expressed as the
equivalent telomerase intensity of the number of cells of MIA
PaCa-2 per microgram
of protein in the tissue samples.“ Significantly different from
groups of normal ducts and adenomas (P < 0.0001).‘ Significantly
different from a group of intraductal papillary and
well-differentiated adenocarcinomas (P < 0.05).“ Tumor stage is
assessed according to UICC-TNM staging (29).
Fig. 2 Relative values of telomerase activity.Relative values of
telomerase activity arc cx-pressed as the equivalent telomerase
intensity of
the number of cells of MIA PaCa-2 per micro-
gram protein of samples. The results are cx-
pressed by means of a box-and-whisker plot anal-
ysis. The botto�n and top edges of the box arelocated at the
sample 25th and 75th percentiles.respectively. The center
horizontal line is drawn
at the sample median. The center vertical lines
from the box extend to a distance of the 10th or90th
percentiles. The relative values of telomeraseactivity in carcinoma
samples arc significantlyhigher than those in other tissue samples
(P <0.0001).
aE
C
C
>
a:
100000
discriminate pancreatic cancer from chronic pancreatitis.
The
present study demonstrated that telomerase was exclusively
activated in the tissues of pancreatic carcinomas while
being
completely repressed in chronic pancreatitis. The future study
of
telomerase activity on cell samples in pancreatic juice
obtained
preoperatively by endoscopic retrograde pancreatography is
warranted.
In regard to the staging of pancreatic cancer, relative te-
lomerase activity tended to be higher in the T1-T, group than
in
the T3-T4 group. In the T3-T4 group, the unique composition
of
the far-advanced pancreatic carcinoma, consisting of a large
amount of fibrous stroma, necrotic tissue, and mucin in some
cases, along with a relatively small number of cancer cells,
may
account for the lower telomerase activity. Telomerase
activity
was significantly higher in the group of intraductal papillary
and
well-differentiated adenocarcinomas when compared to the
group of moderately to poorly differentiated
adenocarcinomas.
Considering that telomerase activity correlates to cellular
im-
mortality, a patient with pancreatic cancer presenting with
high
telomerase activity will have a poor prognosis. It has been
reported that the survival rate of gastric cancer tumors
with
telomerase activity is significantly shorter compared to
gastric
cancer tumors without telomerase activity (12). Similarly,
neu-
roblastoma patients presenting with high telomerase activity
have an unfavorable prognosis compared to cases of
neuroblas-
toma with low telomerase activity (34). To our knowledge.
there
have been no reports of a clear relationship between
histological
differentiation and outcome of pancreatic cancer.
Furthermore,
no previous study has demonstrated an unfavorable prognosis
for intraductal papillary and well-differentiated
adenocarcino-
mas. The group of intraductal papillary and
well-differentiated
adenocarcinomas consisted of a relatively dense cellular
corn-
ponent of carcinoma. On the other hand, the group of moder-
ately to poorly differentiated adenocarcinomas consisted of
rel-
atively abundant stromas. The difference in telomerase
activity
among cancer cell populations may indeed be affected by such
proportional differences between malignant cells and normal
cells.
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998 Telomerase Elevation in Pancreatic Ductal Carcinoma
ACKNOWLEDGMENTSWe are grateful to N. Kinukawa, Department of
Medical Informat-
ics, Kyushu University, for advice on the statistical analysis.
We thank
Professor Sheshadri Narayanan, New York Medical College. for
assist-
ance in the preparation of the manuscript.
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1997;3:993-998. Clin Cancer Res N Suehara, K Mizumoto, T Muta,
et al. to nonmalignant pathological states.Telomerase elevation in
pancreatic ductal carcinoma compared
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