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Advances in Brief |
Laboratory of Experimental Carcinogenesis and Mutagenesis [P. C. C., M. B. T., C. L., H. F. T., C. D. L., R. L.], Laboratory of Experimental Pathology [J. F. M.], NIH, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709; Experimental Pathology Laboratories, Research Triangle Park, North Carolina 27709 [C. M. D., B. W. G.]; and Department of Pathology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 [S. G. M., O. S.]
| ABSTRACT |
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80%. Only COX-1 protein was
immunohistochemically detected in normal intestinal tissue, whereas
both COX-1 and variable levels of COX-2 protein were detected in
polyps. Prostaglandin E2 was increased in polyps compared
with normal tissue, and both COX-1 and COX-2 contributed to the
PGE2 produced. The results indicate that COX-1, as well as
COX-2, plays a key role in intestinal tumorigenesis and that COX-1 may
also be a chemotherapeutic target for nonsteroidal anti-inflammatory
drugs. | Introduction |
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To determine whether COX-1 may also contribute to the development of intestinal cancer, we bred mice disrupted for the Ptgs-1 (9) or Ptgs-2 (10) genes to the Min/+ mouse (16) . The Min/+ mouse contains a truncating mutation in the Apc gene and spontaneously develops intestinal adenomas. In the present study, we used the Min/+ mouse to demonstrate that the deficiency of COX-1, as well as of COX-2, reduces intestinal polyp formation.
| Materials and Methods |
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Determination of Tumor Numbers and Histological Analysis.
To determine the number of intestinal tumors, the entire intestinal
tract was removed, opened longitudinally, and washed with cold saline,
and the proximal, mid, and distal sections of the small intestine,
along with the colon, were spread flat, mucosal surface up, on filter
paper for counting of nodules. Macroscopic nodules were scored with a
limit of detectability of 1 mm. Selected sections of the tract were
fixed in 10% neutral buffered formalin (NBF), paraffin embedded and
histologically sectioned for immunohistochemistry. Swiss rolls
(17)
of intestinal sections from mice of each genotype
were likewise fixed in 10% neutral buffered formalin and sectioned for
microscopic examination to assess correlations between genotype and the
incidence of preneoplastic lesions, as well as the histomorphology of
adenomas. Microscopic examination of Swiss rolls also confirmed that
nodules corresponding to gut-associated lymphoid tissue were few in
number relative to adenoma nodules and did not effect tumor numbers
obtained by macroscopic counting.
Immunohistochemisty Protocol.
Paraffin-embedded sections of intestinal tissue were stained
according to the protocol from the Vectastain ABC Elite kit (Vector
Laboratories, Burlingame, CA). The polyclonal antibodies used were
goat-antimouse COX-1 (1:4000; Santa Cruz Biotechnology, Santa Cruz, CA)
or rabbit-antimouse COX-2 (1:4000; Cayman Chemical, Ann Arbor, MI).
Immunoreactivity was detected with 3,3-diaminobenzidine (Sigma Chemical
Co., St. Louis, MO), and slides were counterstained with Mayers
hematoxylin (Sigma). Intestinal tissues from COX-1(-/-) or
COX-2(-/-) were run as negative controls to check the specificities
of the respective antibodies.
Prostaglandin E2 Analyses.
For PGE2 analysis, normal or tumor tissue was
excised and snap frozen in liquid N2. The frozen
tissues were thawed, weighed, and homogenized in 0.51.5 ml of 50
mM Tris-HCl (pH 7.4) containing 5 µg/ml indomethacin.
Often, it was necessary to pool two to three polyps from a particular
mouse to obtain adequate tissue prior to homogenization. Homogenates
were centrifuged at 1700 x g, 4°C, and the
supernatant was analyzed for PGE2 levels using
the Amersham-Pharmacia Biotech (Piscataway, NJ)
125I-labeled PGE2 RIA.
Statistical Analyses.
For tumor counts and PGE2 levels, ANOVA
procedures were used to assess sex and genotype differences. No
significant differences were observed between males and females.
Therefore, the data were pooled from the two sexes. The Freeman-Tukey
Transformation for Poisson data (18)
was used as a
variance stabilizing logarithmic transformation. Although some degree
of extra Poisson variability was present in the tumor counts, the
Freeman-Tukey transformation was successful in eliminating the
heterogeneity of variances across groups. If overall differences among
genotypes were detected, pairwise comparisons were made by Fishers
LSD test (19)
.
| Results |
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10 months, and Ptgs-1(-/-) mice lived 12
months or longer compared with the 78-month life span of
Ptgs-1(+/+) Min/+ mice. In 1-year-old
Ptgs-1(-/-) Min/+ mice, the numbers of tumors
(2.5 ± 0.8 in proximal; 5.5 ± 2.0 in
mid; 8.8 ± 3.0 in distal small intestines; and
0.5 ± 0.5 in colon) were only slightly increased over
those in 6-month-old mice with equivalent genotypes.
|
10% compared with Ptgs-2(+/+) Min/+ mice
(Fig. 1B)
1 year. Therefore, our observation that COX-2
deficiency causes effects in the Min/+ mouse similar to
those seen by Oshima et al. (15)
in the
Apc716 knockout mouse suggests that the
Ptgs-2, as well as the Ptgs-1, effects observed
in the present study are not limited to the Min/+ mouse.
|
COX-1 Is Immunologically Detected in Normal Tissue Whereas Both
COX-1 and COX-2 Are Detected in Polyps.
Normal and neoplastic tissues from all mouse genotypes were
immunostained with antibodies specific for COX-1 or COX-2. Only COX-1
was detected in normal tissue of all mouse genotypes except from mice
lacking a functional Ptgs-1 gene. COX-1 was localized to the
inner muscular layer, cells in the lamina propria, and a few rare
villous epithelial cells in the mucosa (Fig. 2, a and b)
. This pattern of COX-1 immunoreactivity was similar in
both normal and neoplastic tissue (Fig. 2, c and d)
. Whereas COX-2 protein was generally not detectable in
normal intestinal tissue, localized areas of COX-2 immunostaining were
detected in cells of the lamina propria in many adenomas [except those
from Ptgs-2(-/-) mice; Fig. 2, e and f
]. However, the size of the positive regions and intensity
of COX-2 immunostaining varied from polyp to polyp, with smaller polyps
generally showing less detectable COX-2 protein.
PGE2 Production in Normal Intestinal Tissue and in
Polyps.
To determine the relative contribution of the COX isoforms to
intestinal prostaglandin production, PGE2 was
used as an indicator of prostaglandin synthesis because it is a
prostaglandin that is increased in polyps compared with normal
intestinal tissue (20)
. The data in Fig. 3
compare PGE2 levels in normal distal intestinal
tissue (tissue surrounding the adenomas) and adenomas from
Ptgs-1 and Ptgs-2 Min/+ mice. The data show that
COX-1 is the major isoform responsible for basal
PGE2 production in normal tissue, because
PGE2 levels are reduced by 99% in
Ptgs-1(-/-) mice. PGE2 levels were
increased in polyps compared with normal tissue in the distal intestine
(Fig. 3)
in wild-type mice and the data from the COX-1 and COX2
deficient mice indicate that both COX-1 and COX-2 contribute to
PGE2 production in the polyp. Similar results
were obtained when colonic normal tissue and polyps were compared (data
not shown). In summary, the data show that COX-1 is the major source of
PGE2 in normal tissue and that both COX-1 and
COX-2 contribute to PGE2 production in polyps.
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| Discussion |
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The deficiency of either COX-1 or COX-2 caused similar decreases in
intestinal tumorigenesis in the Min/+ mouse
(i.e., 77 and 84%, respectively; Fig. 1
). Furthermore, it
was observed that both COX-1 and COX-2 contributed to
PGE2 production in polyps (Fig. 3)
.
Simplistically, one possible interpretation of the data may be that it
is the total prostaglandin level in the incipient polyp that is
important for adenoma development, and that decreased prostaglandin
production attributable to the loss of either isoform significantly
reduces tumor formation. In support of this possibility, it has
recently been reported that mice deficient in the
PGE2 receptor, EP1, show
about a 40% decrease in aberrant crypt foci after azoxymethane
treatment (21)
. Furthermore, an EP1
antagonist decreased the number and size of polyps formed in the
Min/+ mouse (21)
. Both COX-1 and COX-2 could
contribute to the production of PGE2, which
interacts with the EP1 receptor. Alternatively,
the COX isoforms could lead to the production of different
prostaglandins and thereby influence tumorigenesis through different
receptor-mediated pathways. As discussed below, it is also possible
that the individual COX isoforms contribute to polyp formation at
different stages of the tumorigenesis process.
Recent studies have provided some insight into possible roles of COX-2
in intestinal tumorigenesis (22)
. Oshima et al.
(15)
demonstrated previously that COX-2 deficiency
decreased intestinal tumorigenesis in an Apc knockout mouse.
Additionally, these authors observed that in Ptgs-2(+/+)
mice COX-2 protein was detectable in the intestinal polyps after they
reached a size of
2 mm. Prescott and White (22)
, in
their discussion of the work of Oshima et al.
(15)
, postulated that COX-2 was up-regulated after the
loss of the wild-type Apc allele and that COX-2-derived
prostaglandins contributed to tumor promotion. The data we obtained
with the COX-2(-/-) Min/+ mouse are essentially the same
as those reported by Oshima et al. (15)
, and
therefore COX-2-derived prostaglandins could also contribute to tumor
promotion in the Min/+ mouse. Similar to Oshima et
al. (15)
, we observed that COX-2 expression was in
the interstitial cells rather than the epithelial cells of the polyp.
It has been reported recently that macrophages in the lamina propria of
the polyps of the Min/+ mouse were responsible for the
increased COX-2 expression (23)
. Therefore, our data, and
those of Oshima et al. (15)
, Hull et
al. (23)
, and Shattuck-Brandt et al.
(24)
raise the question as to whether COX-2 expression is
required in the epithelial tumor cells or whether COX-2-derived
prostaglandins from the interstitial cells at this stage of tumor
development can act by a paracrine mechanism on the neoplastic
epithelial cells.
The possible role(s) of COX-1 in intestinal tumorigenesis have received
less attention than those for COX-2. Our data show that COX-1 is
constitutively expressed in normal intestinal tissue (Fig. 2)
and that
although it is the primary source of prostaglandins as measured by
PGE2 production in intestinal tissue (Fig. 3)
, no
pathology of intestinal tissue was detected in COX-1(-/-) mice
(9)
. However, both COX-1 and COX-2 contribute to
PGE2 levels in the adenoma (Fig. 3)
. Therefore,
COX-1 could exert its effects in the tumorigenesis process both at an
early stage and at later stages in tumor development. In support of an
early role for COX-1, studies have indicated that COX-1 can
metabolically activate procarcinogens to mutagenic intermediates
(3)
, and that aspirin can inhibit this metabolic
activation. Craven and DeRubertis (4)
demonstrated that
aspirin, a more effective inhibitor of COX-1 than COX-2
(7)
, administered at the time of 1,2-dimethylhydrazine
treatment reduced intestinal tumorigenesis by 60%, whereas starting
aspirin administration after the 1,2-dimethylhydrazine had little
effect on tumorigenesis. In addition to the possible activation of
dietary procarcinogens, normal COX-1 metabolism of endogenous
arachidonic acid can lead to the generation of a known mutagen,
malondialdehyde (3)
. Because the Min/+ mouse is
already genetically mutated at one Apc allele, a second
mutagenic event according to the two-hit mechanism of Knudson
(25)
is required. It has been shown that 100% of the
spontaneous polyps in the C57 Bl/6-Min/+ mouse lose the
wild-type Apc allele (16)
. It is possible that
in COX-1(-/-) mice, malondialdehyde production decreases, and that a
second mutagenic event, possibly leading to the loss of the wild-type
allele, is less frequent, and therefore, fewer tumors result.
Alternatively, independent of contributing to mutagen production, COX-1
has been shown to protect colonic stem cells after gamma irradiation.
Cohn et al. (26)
demonstrated that after
in vivo gamma irradiation, COX-1 produced prostaglandins
that significantly enhanced stem cell survival and growth ex
vivo. In the absence of COX-1 in the Min/+ mouse,
genetically damaged cells and/or cells undergoing the loss of the
wild-type Apc allele may have impaired survival and thus
lead to less adenoma formation. However, this possible early role for
COX-1 in intestinal tumorigenesis does not preclude COX-1-derived
prostaglandins from also contributing to tumor promotion.
In the present study, we have demonstrated that both COX-1 and COX-2 deficiencies reduce the tumorigenic responses in the Min/+ mouse. Although our data do not allow us to define separate roles for COX-1 and COX-2, based on our observations and data from previous studies, we have speculated that the two isoforms function via different mechanisms and/or during different stages of the tumorigenesis process. The possibility that the COX isoforms act at different stages during tumor development suggests that COX dual inhibitors may be effective at both early and late stages, whereas selective inhibitors might be more effective when administered either early (COX-1 specific) or late (COX-2 specific). In summary, our data show that genetic ablation of either COX isoform can significantly impact the course of intestinal tumorigenesis in the Min/+ mouse.
| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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1 To whom requests for reprints should be
addressed, at National Institute of Environmental Health Sciences, 111
Alexander Drive, Research Triangle Park, NC 27709. E-mail: chulada@niehs.nih.gov or langenbach{at}niehs.nih.gov ![]()
2 The abbreviations used are: NSAID, nonsteroidal
anti-inflammatory drug; COX, cyclooxygenase; Min,
multiple intestinal neoplasia; Apc, adenomatous
polyposis coli gene; PGE2, prostaglandin E2;
LSD, least significant difference. ![]()
Received 5/19/00. Accepted 7/19/00.
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D. L. Simmons, R. M. Botting, and T. Hla Cyclooxygenase Isozymes: The Biology of Prostaglandin Synthesis and Inhibition Pharmacol. Rev., September 1, 2004; 56(3): 387 - 437. [Abstract] [Full Text] [PDF] |
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P. A. Adegboyega, O. Ololade, J. Saada, R. Mifflin, J. F. Di Mari, and D. W. Powell Subepithelial Myofibroblasts Express Cyclooxygenase-2 in Colorectal Tubular Adenomas Clin. Cancer Res., September 1, 2004; 10(17): 5870 - 5879. [Abstract] [Full Text] [PDF] |
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A. P. Pentland, G. Scott, J. VanBuskirk, C. Tanck, G. LaRossa, and S. Brouxhon Cyclooxygenase-1 Deletion Enhances Apoptosis but Does Not Protect Against Ultraviolet Light-Induced Tumors Cancer Res., August 15, 2004; 64(16): 5587 - 5591. [Abstract] [Full Text] [PDF] |
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M. A. Hull, S. C.W. Ko, and G. Hawcroft Prostaglandin EP receptors: Targets for treatment and prevention of colorectal cancer? Mol. Cancer Ther., August 1, 2004; 3(8): 1031 - 1039. [Abstract] [Full Text] [PDF] |
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M. M. Huycke and H. R. Gaskins Commensal Bacteria, Redox Stress, and Colorectal Cancer: Mechanisms and Models Experimental Biology and Medicine, July 1, 2004; 229(7): 586 - 597. [Abstract] [Full Text] [PDF] |
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S. C Larsson, M. Kumlin, M. Ingelman-Sundberg, and A. Wolk Dietary long-chain n-3 fatty acids for the prevention of cancer: a review of potential mechanisms Am. J. Clinical Nutrition, June 1, 2004; 79(6): 935 - 945. [Abstract] [Full Text] [PDF] |
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C. M. Ulrich, J. Bigler, R. Sparks, J. Whitton, J. G. Sibert, E. L. Goode, Y. Yasui, and J. D. Potter Polymorphisms in PTGS1 (=COX-1) and Risk of Colorectal Polyps Cancer Epidemiol. Biomarkers Prev., May 1, 2004; 13(5): 889 - 893. [Abstract] [Full Text] [PDF] |
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F. G. Bottone Jr, J. M. Martinez, B. Alston-Mills, and T. E. Eling Gene modulation by Cox-1 and Cox-2 specific inhibitors in human colorectal carcinoma cancer cells Carcinogenesis, March 1, 2004; 25(3): 349 - 357. [Abstract] [Full Text] [PDF] |
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D. Golijanin, J.-Y. Tan, A. Kazior, E. G. Cohen, P. Russo, G. Dalbagni, K. J. Auborn, K. Subbaramaiah, and A. J. Dannenberg Cyclooxygenase-2 and Microsomal Prostaglandin E Synthase-1 Are Overexpressed in Squamous Cell Carcinoma of the Penis Clin. Cancer Res., February 1, 2004; 10(3): 1024 - 1031. [Abstract] [Full Text] [PDF] |
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T.-L. Erkinheimo, H. Lassus, P. Finne, B. P. van Rees, A. Leminen, O. Ylikorkala, C. Haglund, R. Butzow, and A. Ristimaki Elevated Cyclooxygenase-2 Expression Is Associated with Altered Expression of p53 and SMAD4, Amplification of HER-2/neu, and Poor Outcome in Serous Ovarian Carcinoma Clin. Cancer Res., January 15, 2004; 10(2): 538 - 545. [Abstract] [Full Text] [PDF] |
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E. Puxeddu, N. Mitsutake, J. A. Knauf, S. Moretti, H. W. Kim, K. A. Seta, D. Brockman, L. Myatt, D. E. Millhorn, and J. A. Fagin Microsomal Prostaglandin E2 Synthase-1 Is Induced by Conditional Expression of RET/PTC in Thyroid PCCL3 Cells through the Activation of the MEK-ERK Pathway J. Biol. Chem., December 26, 2003; 278(52): 52131 - 52138. [Abstract] [Full Text] [PDF] |
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M. ROMANO and J. CLARIA Cyclooxygenase-2 and 5-lipoxygenase converging functions on cell proliferation and tumor angiogenesis: implications for cancer therapy FASEB J, November 1, 2003; 17(14): 1986 - 1995. [Abstract] [Full Text] [PDF] |
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K. Subbaramaiah, T. P. Marmo, D. A. Dixon, and A. J. Dannenberg Regulation of Cyclooxgenase-2 mRNA Stability by Taxanes: EVIDENCE FOR INVOLVEMENT OF p38, MAPKAPK-2, and HuR J. Biol. Chem., September 26, 2003; 278(39): 37637 - 37647. [Abstract] [Full Text] [PDF] |
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R. Salcedo, X. Zhang, H. A. Young, N. Michael, K. Wasserman, W.-H. Ma, M. Martins-Green, W. J. Murphy, and J. J. Oppenheim Angiogenic effects of prostaglandin E2 are mediated by up-regulation of CXCR4 on human microvascular endothelial cells Blood, September 15, 2003; 102(6): 1966 - 1977. [Abstract] [Full Text] [PDF] |
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H. Takeda, M. Sonoshita, H. Oshima, K.-i. Sugihara, P. C. Chulada, R. Langenbach, M. Oshima, and M. M. Taketo Cooperation of Cyclooxygenase 1 and Cyclooxygenase 2 in Intestinal Polyposis Cancer Res., August 15, 2003; 63(16): 4872 - 4877. [Abstract] [Full Text] [PDF] |
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H. L. Kettunen, A. S. L. Kettunen, and N. E. Rautonen Intestinal Immune Responses in Wild-Type and ApcMin/+ Mouse, a Model for Colon Cancer Cancer Res., August 15, 2003; 63(16): 5136 - 5142. [Abstract] [Full Text] [PDF] |
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H. Nishihara, S. Kizaka-Kondoh, P. A. Insel, and L. Eckmann Inhibition of apoptosis in normal and transformed intestinal epithelial cells by cAMP through induction of inhibitor of apoptosis protein (IAP)-2 PNAS, July 22, 2003; 100(15): 8921 - 8926. [Abstract] [Full Text] [PDF] |
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G. Hawcroft, S. H. Gardner, and M. A. Hull Activation of Peroxisome Proliferator-Activated Receptor gamma Does Not Explain the Antiproliferative Activity of the Nonsteroidal Anti-Inflammatory Drug Indomethacin on Human Colorectal Cancer Cells J. Pharmacol. Exp. Ther., May 1, 2003; 305(2): 632 - 637. [Abstract] [Full Text] [PDF] |
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P. Klatt and M. Serrano Engineering cancer resistance in mice Carcinogenesis, May 1, 2003; 24(5): 817 - 826. [Abstract] [Full Text] [PDF] |
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T. Kawamori, N. Uchiya, T. Sugimura, and K. Wakabayashi Enhancement of colon carcinogenesis by prostaglandin E2 administration Carcinogenesis, May 1, 2003; 24(5): 985 - 990. [Abstract] [Full Text] [PDF] |
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N. S. Cutler, R. Graves-Deal, B. J. LaFleur, Z. Gao, B. M. Boman, R. H. Whitehead, E. Terry, J. D. Morrow, and R. J. Coffey Stromal Production of Prostacyclin Confers an Antiapoptotic Effect to Colonic Epithelial Cells Cancer Res., April 15, 2003; 63(8): 1748 - 1751. [Abstract] [Full Text] [PDF] |
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H. Fujino, W. Xu, and J. W. Regan Prostaglandin E2 Induced Functional Expression of Early Growth Response Factor-1 by EP4, but Not EP2, Prostanoid Receptors via the Phosphatidylinositol 3-Kinase and Extracellular Signal-regulated Kinases J. Biol. Chem., March 28, 2003; 278(14): 12151 - 12156. [Abstract] [Full Text] [PDF] |
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R. A. Gupta, L. V. Tejada, B. J. Tong, S. K. Das, J. D. Morrow, S. K. Dey, and R. N. DuBois Cyclooxygenase-1 is Overexpressed and Promotes Angiogenic Growth Factor Production in Ovarian Cancer Cancer Res., March 1, 2003; 63(5): 906 - 911. [Abstract] [Full Text] [PDF] |
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C. W. Houchen, M. A. Sturmoski, S. Anant, R. M. Breyer, and W. F. Stenson Prosurvival and antiapoptotic effects of PGE2 in radiation injury are mediated by EP2 receptor in intestine Am J Physiol Gastrointest Liver Physiol, March 1, 2003; 284(3): G490 - G498. [Abstract] [Full Text] [PDF] |
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S. Tokudome, Y. Yokoyama, T. Kamiya, K. Seno, H. Okuyama, K. Kuriki, J. Cheng, T. Nakamura, T. Fujii, H. Ichikawa, et al. Rationale and Study Design of Dietary Intervention in Patients Polypectomized for Tumors of the Colorectum Jpn. J. Clin. Oncol., December 1, 2002; 32(12): 550 - 553. [Abstract] [Full Text] [PDF] |
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B. S. Zweifel, T. W. Davis, R. L. Ornberg, and J. L. Masferrer Direct Evidence for a Role of Cyclooxygenase 2-derived Prostaglandin E2 in Human Head and Neck Xenograft Tumors Cancer Res., November 15, 2002; 62(22): 6706 - 6711. [Abstract] [Full Text] [PDF] |
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T. Kitamura, T. Kawamori, N. Uchiya, M. Itoh, T. Noda, M. Matsuura, T. Sugimura, and K. Wakabayashi Inhibitory effects of mofezolac, a cyclooxygenase-1 selective inhibitor, on intestinal carcinogenesis Carcinogenesis, September 1, 2002; 23(9): 1463 - 1466. [Abstract] [Full Text] [PDF] |
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H. F. Tiano, C. D. Loftin, J. Akunda, C. A. Lee, J. Spalding, A. Sessoms, D. B. Dunson, E. G. Rogan, S. G. Morham, R. C. Smart, et al. Deficiency of Either Cyclooxygenase (COX)-1 or COX-2 Alters Epidermal Differentiation and Reduces Mouse Skin Tumorigenesis Cancer Res., June 1, 2002; 62(12): 3395 - 3401. [Abstract] [Full Text] [PDF] |
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E. T. Hawk, J. L. Viner, A. Dannenberg, and R. N. DuBois COX-2 in Cancer--A Player That's Defining the Rules J Natl Cancer Inst, April 17, 2002; 94(8): 545 - 546. [Full Text] [PDF] |
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N. Kundu and A. M. Fulton Selective Cyclooxygenase (COX)-1 or COX-2 Inhibitors Control Metastatic Disease in a Murine Model of Breast Cancer Cancer Res., April 1, 2002; 62(8): 2343 - 2346. [Abstract] [Full Text] [PDF] |
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M. Mutoh, K. Watanabe, T. Kitamura, Y. Shoji, M. Takahashi, T. Kawamori, K. Tani, M. Kobayashi, T. Maruyama, K. Kobayashi, et al. Involvement of Prostaglandin E Receptor Subtype EP4 in Colon Carcinogenesis Cancer Res., January 1, 2002; 62(1): 28 - 32. [Abstract] [Full Text] [PDF] |
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M. B. Hansen-Petrik, M. F. McEntee, B. Jull, H. Shi, M. B. Zemel, and J. Whelan Prostaglandin E2 Protects Intestinal Tumors from Nonsteroidal Anti-inflammatory Drug-induced Regression in ApcMin/+ Mice Cancer Res., January 1, 2002; 62(2): 403 - 408. [Abstract] [Full Text] [PDF] |
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G. Hawcroft, M. D'Amico, C. Albanese, A. F. Markham, R. G. Pestell, and M. A. Hull Indomethacin induces differential expression of {beta}-catenin, {gamma}-catenin and T-cell factor target genes in human colorectal cancer cells Carcinogenesis, January 1, 2002; 23(1): 107 - 114. [Abstract] [Full Text] [PDF] |
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K. Yoshimatsu, D. Golijanin, P. B. Paty, R. A. Soslow, P.-J. Jakobsson, R. A. DeLellis, K. Subbaramaiah, and A. J. Dannenberg Inducible Microsomal Prostaglandin E Synthase Is Overexpressed in Colorectal Adenomas and Cancer Clin. Cancer Res., December 1, 2001; 7(12): 3971 - 3976. [Abstract] [Full Text] [PDF] |
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M. T. Yip-Schneider, C. J. Sweeney, S.-H. Jung, P. L. Crowell, and M. S. Marshall Cell Cycle Effects of Nonsteroidal Anti-Inflammatory Drugs and Enhanced Growth Inhibition in Combination with Gemcitabine in Pancreatic Carcinoma Cells J. Pharmacol. Exp. Ther., September 1, 2001; 298(3): 976 - 985. [Abstract] [Full Text] |
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X. Chen and C. S. Yang Esophageal adenocarcinoma: a review and perspectives on the mechanism of carcinogenesis and chemoprevention Carcinogenesis, August 1, 2001; 22(8): 1119 - 1129. [Abstract] [Full Text] [PDF] |
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K. Saukkonen, O. Nieminen, B. van Rees, S. Vilkki, M. Harkonen, M. Juhola, J.-P. Mecklin, P. Sipponen, and A. Ristimaki Expression of Cyclooxygenase-2 in Dysplasia of the Stomach and in Intestinal-type Gastric Adenocarcinoma Clin. Cancer Res., July 1, 2001; 7(7): 1923 - 1931. [Abstract] [Full Text] [PDF] |
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C. H. Liu, S.-H. Chang, K. Narko, O. C. Trifan, M.-T. Wu, E. Smith, C. Haudenschild, T. F. Lane, and T. Hla Overexpression of Cyclooxygenase-2 Is Sufficient to Induce Tumorigenesis in Transgenic Mice J. Biol. Chem., May 18, 2001; 276(21): 18563 - 18569. [Abstract] [Full Text] [PDF] |
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R. C. Mifflin, J. I. Saada, J. F. Di Mari, P. A. Adegboyega, J. D. Valentich, and D. W. Powell Regulation of COX-2 expression in human intestinal myofibroblasts: mechanisms of IL-1-mediated induction Am J Physiol Cell Physiol, April 1, 2002; 282(4): C824 - C834. [Abstract] [Full Text] [PDF] |
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