telomerase elevation in pancreatic ductal carcinoma ...creatic ductal carcinomas were 100 and 80%,...

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.



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.



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


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



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.




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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telomerase elevation in pancreatic ductal carcinoma ...creatic ductal carcinomas were 100 and 80%,...

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