(American Journal of Pathology. 2001;158:849-853.)
© 2001 American Society for Investigative Pathology
Expression of Cyclooxygenase-2 in Human Transitional Cell Carcinoma of the Urinary Bladder
Ari Ristimäki*
,
Outi Nieminen
,
Kirsi Saukkonen
,
Kristina Hotakainen§,
Stig Nordling* and
Caj Haglund
From the Departments of Pathology,*
Obstetrics and
Gynecology,
Surgery,
and Clinical Chemistry,§
Helsinki University
Central Hospital and the Haartman Institute, University of Helsinki,
Helsinki, Finland
 |
Abstract
|
|---|
Recent studies suggest that expression of cyclooxygenase-2 (Cox-2)
is elevated in transitional cell carcinoma (TCC) of the urinary bladder
and that inhibition of Cox-2 activity suppresses bladder cancer in
experimental animal models. We have investigated the expression of
Cox-2 protein in human TCCs (n = 85), in
in situ carcinomas (Tis) of the urinary bladder
(n = 17), and in nonneoplastic urinary
bladder samples (n = 16) using
immunohistochemistry. Cox-2 immunoreactivity was detected in 66% (67
of 102) of the carcinomas, whereas only 25% (4 of 16) of the
nonneoplastic samples were positive (P < 0.005).
Cox-2 immunoreactivity localized to neoplastic cells in the carcinoma
samples. The rate of positivity was the same in invasive (T13;
70%, n = 40) and in noninvasive (Tis and
Ta; 65%, n = 62) carcinomas, but
noninvasive tumors had a higher frequency (32%) of homogenous pattern
of staining (>90% of the tumor cells positive) than the invasive
carcinomas (10%) (P < 0.05). However,
several invasive TCCs exhibited the strongest intensity of Cox-2
staining in the invading cells, whereas other parts of the
tumor were virtually negative. Finally, strong Cox-2 positivity
was also found in nonneoplastic ulcerations (2 of 2) and in
inflammatory pseudotumors (2 of 2), in which the
immunoreactivity localized to the nonepithelial cells. Taken
together, our data suggest that Cox-2 is highly expressed in
noninvasive bladder carcinomas, whereas the highest expression
of invasive tumors associated with the invading cells, and that
Cox-2 may also have a pathophysiological role in nonneoplastic
conditions of the urinary bladder, such as ulcerations and
inflammatory pseudotumors.
 |
Introduction
|
|---|
Transitional cell carcinoma (TCC) of
the urinary bladder is the third most common cancer in men and the 15th
most common cancer in women accounting for 6.2 and 2.0% of the
annually recorded cancer cases in Finland, respectively.1
TCC-related deaths are mainly caused by the invasive type of the
disease. However, the more frequent form of this carcinoma is either
noninvasive or superficially invasive disease, which is usually
curable, but demonstrates a challenge to the clinician because of its
recurrent nature. Thus, more effective therapies are needed to prevent
recurrence of superficial TCC and to inhibit progression of noninvasive
tumors to invasive carcinomas.
Epidemiological studies suggest that the use of aspirin and other
nonsteroid anti-inflammatory drugs (NSAIDs) is associated with a
reduced risk of gastrointestinal cancer.2,3
In addition,
NSAIDs can induce regression of premalignant colorectal polyps in
patients with familial adenomatous polyposis, and inhibit
carcinogenesis in several rodent models including those of bladder
cancer.3,4
The best known target of NSAIDs is
cyclooxygenase (Cox), the rate-limiting enzyme in the conversion of
arachidonic acid to prostanoids.5,6
Two Cox genes have
been cloned (Cox-1 and Cox-2) that share >60% identity at the amino
acid level and have similar enzymatic activities. The most striking
difference between the Cox genes is in the regulation of their
expression. Although Cox-1 is constitutively expressed and the
expression is not usually regulated, expression of Cox-2 is low or not
detectable in most healthy tissues, but can be highly induced in
response to cell activation by hormones, proinflammatory cytokines,
growth factors, and tumor promoters. Thus, the pathophysiological role
of Cox-2 has been connected to inflammation, reproduction, and
carcinogenesis.5-7
Recent animal studies suggest that Cox-2 expression, but not that of
Cox-1, is elevated in bladder cancer.8,9
Furthermore,
NSAIDs that inhibit either preferentially or selectively Cox-2 are
chemopreventive against bladder cancer in the rat.10,11
Elevated Cox-2 expression has been described in several human
malignancies.5,7,12
However, in the case of bladder
cancer, the data are inconsistent in respect of the presence of Cox-2
expression in in situ carcinomas (Tis), and whether Cox-2 is
expressed in low-grade and in noninvasive TCCs.13-15
The
purpose of this study was to investigate the expression of Cox-2 in
both noninvasive and invasive TCC and in nonneoplastic lesions of the
bladder using immunohistochemistry and a Cox-2-specific monoclonal
antibody combined with the use of appropriate control experiments.
 |
Materials and Methods
|
|---|
Patient Samples
Formalin-fixed and paraffin-embedded urinary-bladder tissue
specimens from patients with invasive TCC (T1, T2, and T3;
n = 40), noninvasive carcinomas (Tis or Ta;
n = 62), and 16 nonneoplastic conditions (eight
cystitis, two ulcerations, two inflammatory pseudotumors, and four
samples with normal histology) were obtained from the files of the
Department of Pathology, Helsinki University Central Hospital (Table 1)
. The age of the carcinoma patients was
71 ± 13 years (mean ± SD; range, 42 to 95 years) and that
of patients with nonneoplastic lesions 67 ± 18 years (range, 25
to 94 years). Of the TCC patients 25 were women and 77 men, and in the
nonneoplastic group there was three women and 13 men. Twenty of the
specimens were taken at radical cystectomy and the rest were
transurethral biopsies. Grade (G13) of the tumor was determined
according to the World Health Organization
classification,16
and by the more recent (low and high
grade) World Health Organization/International Society of Urologic
Pathologists consensus classification for the urothelial
neoplasms.17
All samples were reassessed by a pathologist
(SN).
Immunohistochemistry
The specimens were sectioned (4 µm), deparaffinized, and
microwaved for 4 x 5 minutes at 700 W in 0.01 mol/L Na-citrate
buffer (pH 6.0) for antigen retrieval. The slides were then immersed in
0.6% hydrogen peroxide in methanol for 30 minutes to block endogenous
peroxidase activity and in blocking solution [1.5:100 normal horse
serum in phosphate-buffered saline (PBS)] for 15 minutes to block
unspecific binding sites. Immunostaining was performed with
Cox-2-specific anti-human monoclonal antibody (160112; Cayman Chemical
Co., Ann Arbor, MI) in a dilution of 1:200 (2.5 µg/ml) in PBS
containing 0.1% sodium azide and 0.5% bovine serum albumin at room
temperature overnight. Then the sections were treated with biotinylated
horse anti-mouse immunoglobulin (1:200; Vector Laboratories Inc.,
Burlingame, CA) and avidin-biotin peroxidase complex (Vectastain
ABComplex, Vector Laboratories). The peroxidase staining was visualized
with 3-amino-9-ethylcarbazole (Sigma Chemical Co., St. Louis, MO), and
the sections were counterstained with Mayers hematoxylin. The
specificity of the antibody was determined by pre-adsorption of the
primary antibody with human Cox-2 control peptide (1 to 10 µg/ml,
Cayman Chemical) for 1 hour at room temperature before the staining
procedure. An
-smooth muscle cell actin peptide (50 µg/ml; DAKO,
Glostrup, Denmark) was used as a non-Cox-2 peptide.
The intensity of the Cox-2 immunoreactivity was graded negative, weakly
positive, or strongly positive, reflecting both the intensity of
staining as well as the amount of positive cells in consensus of two
investigators (SN and AR). In addition, the proportion of
Cox-2-positive tumor cells was estimated (<10%, 10 to 90%, >90%).
Statistical Analysis
Statistical significance was calculated using the Fishers exact
test, and P < 0.05 was selected as the statistically
significant value.
 |
Results
|
|---|
Expression of Cox-2 protein was investigated in 102 carcinoma
specimens and in 16 nonneoplastic samples of the human urinary bladder
using immunohistochemistry (Figure 1)
.
Cox-2 immunoreactivity was detected in 66% (67 of 102) of the
carcinomas (Table 1)
, whereas only 25% (4 of 16) of the nonneoplastic
samples were positive (P < 0.005). Cox-2
immunoreactivity localized almost exclusively to the neoplastic cells
in the TCCs, whereas the stroma of the tumors was negative (Figure 1, G to L)
. Although 19% of the TCC specimens stained with high intensity,
none of the nonneoplastic specimens showed strong staining in the
epithelial cell compartment. The rate of positivity was the same in
invasive (T13; 70%, n = 40) and in noninvasive (Tis
or Ta; 65%, n = 62) TCCs. However, only 24% (24 of
102) of the TCCs exhibited homogenous staining (>90% of the tumor
cells positive), suggesting that the staining pattern of Cox-2 is
relatively heterogeneous. Interestingly, noninvasive specimens
exhibited a higher frequency (32%, 20 of 62) of homogenous staining
than the invasive TCCs (10%, 4 of 40) (P <
0.05). Furthermore, several invasive TCCs exhibited the strongest
intensity of Cox-2 staining in the invading cells (1 of 45 of T1, 2 of
12 of T2, and 4 of 7 of T3), whereas other parts of the tumor expressed
low or undetectable levels of the protein. No statistically significant
difference in the Cox-2 positivity was found between different grades
of the TCCs when either World Health Organization classification (Table 1)
or World Health Organization/ISUP consensus classification were used
(low-grade tumors were 61% and high-grade neoplasms 69% positive for
Cox-2). In addition to the neoplastic epithelial cells of the TCCs,
strong Cox-2 positivity was present at sites of nonneoplastic
ulcerations (2 of 2) and in inflammatory pseudotumors (2 of 2), in
which the immunoreactivity localized to the nonepithelial cells (Figure 1, M to P)
. The pattern of the Cox-2 immunoreactivity in both
neoplastic and nonneoplastic cells was of diffuse cytoplasmic type with
occasional perinuclear staining (Figure 1; G, I, and L
). The
specificity of the monoclonal antibody was confirmed by staining the
specimens with and without pre-adsorption with the antigenic peptide,
which blocked virtually all immunoreactivity obtained by the antibody
(Figure 1
and data not shown). A peptide unrelated to Cox-2 did not
reduce the immunoreactivity obtained by the monoclonal antibody.

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|
Figure 1. Immunohistochemical detection of Cox-2 protein in the human urinary
bladder specimens using a Cox-2-specific monoclonal antibody.
A: Normal transitional cell epithelium was negative or
stained with weak intensity (B,
pre-adsorption control using an antigenic
peptide). C to L: Cox-2
immunoreactivity localized to the neoplastic cells in the TCC
specimens, but tumor stroma remained negative. C: In
situ carcinoma (D, the
pre-adsorption control). E:
Noninvasive (Ta)
carcinoma (F, the pre-adsorption
control). G: Invasive
(T1) carcinoma
(H, the pre-adsorption
control). I: Invading cells of a T3
carcinoma (J, the pre-adsorption
control). K and L: Cox-2
positivity in an invasive
(T3) carcinoma, whereas
normal transitional cell epithelial cells
(asterisks)
remained essentially negative. M to P: Strong
Cox-2 positivity at sites of nonneoplastic ulcerations and in
inflammatory pseudotumors, in which the immunoreactivity localized to
the nonepithelial cells. M: Ulceration
(N, the pre-adsorption
control). O: Inflammatory pseudotumor
(P, the pre-adsorption
control). Original magnifications: x600
(AJ and LP
) and x200
(K).
|
|
 |
Discussion
|
|---|
Our data indicate that Cox-2 is expressed in 65% of human TCCs
(Ta and T14) as detected by immunohistochemistry. The Cox-2
immunoreactivity localized to the neoplastic cells, whereas the tumor
stroma was negative. Importantly, all immunoreactive signal obtained by
the Cox-2-specific monoclonal antibody was blocked by the antigenic
Cox-2 peptide, but not by an unrelated peptide. Our data are consistent
with previously published reports that indicate that 34 to 84% of TCCs
are positive for Cox-2 as detected by immunohistochemistry or
immunoblotting.13-15
Furthermore, it has been reported
that no Cox-2 expression is evident in nonneoplastic epithelium of the
human, rodent, or canine urine bladder,8,9,13,15
although
one report indicated a relatively high frequency (53%) of Cox-2
expression in nonneoplastic epithelium adjacent to the
tumor.13
We found that the normal transitional cell
epithelium was virtually negative for Cox-2 in both nonneoplastic and
neoplastic specimens. However, we did find strong expression of Cox-2
at sites of nonneoplastic ulcerations and in inflammatory pseudotumors,
but in contrast to the carcinomas, this injury- and
inflammation-associated Cox-2 expression localized to the nonepithelial
(inflammatory and connective tissue) cells. Thus, although the stroma
of the bladder carcinomas was negative for Cox-2, we were able to
detect Cox-2 expression in the stromal cells when they were
appropriately activated. Because expression of Cox-2 has been
associated with ulcer healing in the gastrointestinal tract and its
expression is enhanced by various proinflammatory agents,5
expression of Cox-2 in nonneoplastic bladder lesions may be related to
healing process present at the site of ulceration and because of
inflammatory activity in pseudotumors.
The chemopreventive effect of NSAIDs may be targeted to early lesions,
because they induce regression of premalignant colorectal polyps in
patients with familial adenomatous polyposis and in experimental animal
models of this disease.3,7,18
Cox-2 is also expressed in
epithelial cells of preneoplastic dysplasias and in situ
carcinomas of the stomach (unpublished results),19, 20
esophagus,21-23
and lung.24,25
Furthermore,
it is expressed in chemically induced preneoplastic lesions of the lung
and in the urinary bladder of the rat.8,26
However,
although it is the carcinoma cells that express the highest level of
Cox-2 in colorectal cancer, Cox-2 seems to localize to the stromal and
to a lesser extent to the epithelial cells in colonic
adenomas.27-29
We found that Cox-2 is expressed in 71%
of the Tis and in 60% of the Ta carcinomas. This is consistent with
data published by Mohammed and colleagues13
and by
Shirahama,15
who found 75 and 93% of Tis carcinomas to be
positive for Cox-2 as detected by immunohistochemistry and by
immunoblotting, respectively. However, our data differ from those
published by Kömhoff and colleagues,14
who did not
detect any Cox-2 expression in noninvasive (Ta) or low-grade TCCs. In
fact, we found a higher frequency of homogenous Cox-2 staining in the
Tis and Ta tumors when compared to the invasive carcinomas.
Discrepancies of the immunohistochemistry data may depend on the use of
different antibodies and/or staining methods that affect both
sensitivity and specificity. A more detailed description about the
performance of different Cox-2 antibodies is beyond the scope of this
paper. However, in respect of invasive carcinomas, we did find
expression of Cox-2 to be high in invading cells of the invasive
tumors, even when the rest of the tumor is negative for Cox-2.
Interestingly, expression of Cox-2 may be related to invasion and
metastasis of carcinomas,30-33
which could potentially be
connected to increased production and activation of matrix
metalloproteinases as shown by overexpression of Cox-2 in cancer cell
lines.34,35
All this indicates that Cox-2 is highly expressed in noninvasive TCCs,
and that it may contribute to the invasive potential of more advanced
carcinomas. Because inhibition of Cox-2 is chemopreventive in animal
models of urinary bladder cancer,11
further studies are
required to evaluate whether Cox-2-targeted therapy might prove to be
effective against human TCC.
 |
Acknowledgements
|
|---|
We thank Kaija Antila, Tuija Hallikainen, Elina Laitinen, and Sari
Nieminen for excellent technical assistance; and Bastiaan van Rees for
critical reading of the manuscript.
 |
Footnotes
|
|---|
Address reprint requests to Dr. Ari Ristimäki, Department of Obstetrics and Gynecology, Helsinki University Central Hospital, P.O. Box 140, FIN-00029 Helsinki, Finland. E-mail: ari.ristimaki{at}hus.fi
Supported by the Helsinki University Central Hospital Research Funds, the Finnish Cancer Foundation, and Finska Läkaresällskapet. K. S. received support from the Helsinki University Biomedical Graduate School.
O. N. and K. S. contributed equally to this work.
Accepted for publication November 17, 2000.
 |
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C. Denkert, M. Kobel, S. Pest, I. Koch, S. Berger, M. Schwabe, A. Siegert, A. Reles, B. Klosterhalfen, and S. Hauptmann
Expression of Cyclooxygenase 2 Is an Independent Prognostic Factor in Human Ovarian Carcinoma
Am. J. Pathol.,
March 1, 2002;
160(3):
893 - 903.
[Abstract]
[Full Text]
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A. Ristimaki, A. Sivula, J. Lundin, M. Lundin, T. Salminen, C. Haglund, H. Joensuu, and J. Isola
Prognostic Significance of Elevated Cyclooxygenase-2 Expression in Breast Cancer
Cancer Res.,
February 1, 2002;
62(3):
632 - 635.
[Abstract]
[Full Text]
[PDF]
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K. Salmenkivi, C. Haglund, A. Ristimaki, J. Arola, and P. Heikkila
Increased Expression of Cyclooxygenase-2 in Malignant Pheochromocytomas
J. Clin. Endocrinol. Metab.,
November 1, 2001;
86(11):
5615 - 5619.
[Abstract]
[Full Text]
[PDF]
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