| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Molecular Biology and Genetics |
Departments of Medicine [H. S., J. S., R. N. D.] and Cell Biology [R. N. D.], Vanderbilt-Ingram Cancer Center, Vanderbilt University Medical Center, Department of Veterans Affairs Medical Center, Nashville, Tennessee 37232
 |
ABSTRACT |
|---|
 Top ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
|
INTRODUCTION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
50% of colorectal carcinomas (1)
. Oncogenic mutations in Ras result in activation of downstream signaling proteins including Raf/MEK/ERKs3
(2
, 3)
, Raf-independent signaling proteins that belong to the Rho family (4
, 5)
, and the PI3K/Akt/PKB pathway (6
, 7)
. A specific subset of genes is subsequently modulated, which results in oncogenic Ras transformation (8, 9, 10)
. Prostaglandin endoperoxide synthase-2 (Ptgs-2), commonly referred to as cyclooxygenase-2 (COX-2), is a target of the Ras signaling pathway. Expression of mutated Ha-Ras results in morphological transformation associated with rapid induction of COX-2 in fibroblasts (11) and intestinal epithelial cells (10) . The induction of COX-2 expression by Ras involves both transcriptional and posttranscriptional regulation. Although the precise role of COX-2 in Ras-mediated transformation is not clear, evidence is mounting to indicate that COX-2 expression provides a growth and survival advantage to intestinal epithelial cells (12, 13, 14) .
The serine/threonine kinase Akt (or Akt/PKB) is a direct downstream effector of PI3K (15 , 16) . Akt/PKB can be modulated by multiple intracellular signaling pathways and acts as a transducer for many pathways initiated by growth factor receptors that activate PI3K (reviewed in Ref. 17 ). Akt/PKB regulates gene transcription by directly or indirectly modifying phosphorylation of transcription factors (18, 19, 20, 21, 22, 23, 24) . Activation of the PI3K/Akt/PKB pathway is important in Ras transformation of mammalian cells and essential for Ras-induced cytoskeletal reorganization (6) . The PI3K/Akt/PKB signaling pathway plays a critical role in R-Ras-mediated transformation, adhesion, and cell survival (7) . Evidence suggests that the PI3K/Akt/PKB pathway promotes growth factor-mediated cell survival and inhibits apoptosis (25) by modifying the antiapoptotic and proapoptotic activities of members of the Bcl-2 gene family (26 , 27) . These observations strongly suggest that the PI3K/Akt/PKB pathway is oncogenic and involved in the neoplastic transformation of mammalian cells.
In the present study, we sought to elucidate the role of Akt/PKB in K-Ras-mediated induction of COX-2 in intestinal epithelial cells. Our results indicate that expression of oncogenic K-Ras activates the Raf/MEK/ERK and PI3K/Akt/PKB pathways. Both MEK/ERK and Akt/PKB activities are required for K-Ras-mediated induction of COX-2. The activation of MEK is essential for both increased transcription and stability of COX-2 mRNA, whereas Akt/PKB activity is largely responsible for the stabilization of COX-2 mRNA.
|
MATERIALS AND METHODS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Northern Blot Analysis.
For determination of mRNA stability, IEC-iK-Ras cells were treated with vehicle or IPTG for 48 h, and then the transcription was stopped by addition of 100 µM of DRB (Sigma Chemical Co., St. Louis, MO). RNA samples were extracted, separated on formaldehyde-agarose gels, and blotted on to nitrocellulose membranes as previously described (11)
. The blots were hybridized with cDNA probes labeled with [
-32P]dCTP by random primer extension (Stratagene) and then subjected to autoradiography. rRNA signals at 18S were used as controls to determine integrity of RNA and equality of the loading.
Immunoblot Analysis and Antibodies.
Immunoblot analysis was performed as previously described (28)
. Cells were lysed for 30 min in radioimmunoprecipitation assay buffer (1x PBS, 1% NP40, 0.5% sodium deoxycholate, 0.1% SDS, 10 mg/ml phenylmethyl-sulfonyl fluoride, 10 µg/ml aprotinin, 1 mM sodium orthovanadate). Cell lysates were denatured and fractionated by SDS-PAGE, and after electrophoresis the proteins were transferred to nitrocellulose membranes. The filters were then probed with the indicated antibodies, developed by the enhanced chemiluminescence system (ECL; Amersham, Arlington Heights, IL). The anti-pan Ras antibody was purchased from Calbiochem (La Jolla, CA). The anti-COX-2 antibody was purchased from Santa Cruz Biotechnology (Santa Cruz, CA). The antiphosphorylated (serine 473) Akt antibody was obtained from New England Biolabs (Beverly, MA) and the antiactive ERK1/2 antibody was from Promega (Madison, WI). The anti-ß-actin antibody was purchased from Sigma.
Ectopic Expression of Akt.
To establish the IEC-iK-Ras/Akt-K179M cell line, stable transfection was performed using Lipofectin (Life Technologies, Inc.). A 1.5-kb HindIII-BamHI fragment containing the HA-tagged dominant negative Akt-K179M cDNA (a gift from Dr. Philip N. Tsichlis, Thomas Jefferson University, Philadelphia, PA) was ligated into the eukaryotic expression vector pZeoSV2(+) (Invitrogen, Carlsbad, CA). The resultant pZeoSV2/Akt-K179M vector was then transfected into the IEC-iK-Ras cells and selected in DMEM containing hygromycin, neomycin, and zeocin (250 µg/ml) to generate the IEC-iK-Ras/Akt-K179M clones.
ERK Kinase Assay.
p42/44 MAP kinase activity was measured by determining the transfer of the phosphate group of ATP to a peptide that is a highly specific substrate for p42/44 MAP kinase according to the manufacturer’s instructions (BIOTRAK system; Amersham).
Akt Assay.
For determination of Akt kinase activity we used the Akt kinase assay kit produced by New England Biolabs, according to the manufacturer’s instructions. IEC-iK-Ras cells were treated with IPTG and then lysed at the indicated times. Akt was immunoprecipitated using a monospecific Akt antibody. The immunoprecipitate was then incubated with a GSK-3 fusion protein in the presence of ATP. Phosphorylation of GSK-3 was measured by Western blotting using an anti-phospho-GSK-3/ß (Ser21/9) antibody.
Transfection of Reporter Constructs.
The assays to determine activity of the COX-2 promoter and stability of COX-2 3' UTR are described elsewhere (10)
. To achieve stable transfection, a reporter construct containing the 5'-flanking region of the human COX-2 gene (phPES2-1432/+59, a gift from Dr. Hiroyasu Inoue, National Cardiovascular Center Research Institute, Osaka, Japan; Ref. 29
) or COX-2 3' UTR (pcDNA3/Luc+3' UTR, a gift from Drs. Dan Dixon and Stephen Prescott, University of Utah, Salt Lake City; Ref. 10
, 30
) was transfected into IEC-iK-Ras cells, which are referred to as IEC-iK-Ras/COX-2 5'-luc or IEC-iK-Ras/luc-COX-2 3' UTR cells. Transfected cells were selected by growth in media containing neomycin (600 µg/ml), hygromycin (150 µg/ml), and zeocin (250 µg/ml). Pooled clones were evaluated for luciferase activity. Firefly luciferase values were standardized to the protein concentration, and the data are presented as mean ± SE of assays performed in quadruplicate.
For transient transfections, cells were cotransfected with 0.5 µg of one of the COX-2 firefly luciferase constructs (phPES2-1432/+59 or pcDNA3/Luc+3' UTR) and 1 ng of the pRL-CMV plasmid containing the CMV immediate-early enhancer/promoter region upstream of the renilla luciferase gene (Promega) along with 0.5 µg of Akt expression vectors (myristylated form of Akt-myr or Akt-K179M cDNA, gifts from Dr. Philip N. Tsichlis) or pSG5-
p85 (a gift from Dr. Bart Vanhaesebroeck, Ludwig Institute for Cancer Research, London, United Kingdom). Transfected cells were cultured for 24 h and then lysed in lysis buffer (Promega). Twenty µl of lysate were used for both the firefly and renilla luciferase readings, which were measured using a Dual-Luciferase Reporter assay system (Promega). Firefly luciferase values were standardized to renilla values.
|
RESULTS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
50% of colorectal carcinomas (1)
. To investigate the phenotypic alterations that result from K-Ras-mediated transformation, a conditionally transformed IEC line was established, in which expression of mutated K-RasVal12 can be induced (referred to here as IEC-iK-Ras). IEC-iK-Ras cells displayed a nontransformed morphology similar to parental IEC-6 cells when grown in normal medium (Fig. 1A)
. Treatment of cells with 5 mM IPTG induced the expression of mutated K-Ras. The levels of Ras protein increased slowly up to 12 h and reached a peak at 48 h after addition of IPTG (Fig. 1B)
. Morphological transformation of the IEC-iK-Ras cells was observed between 48 and 72 h after initiation of IPTG treatment. During this interval, cell-cell contact inhibition was lost, and the cells acquired a spindly appearance, growing in overlapping clusters. Both IEC-6 and uninduced IEC-iK-Ras cells were unable to grow in an anchorage-independent fashion. However, in the presence of IPTG, IEC-iK-Ras cells rapidly formed colonies in soft agarose (Fig. 1C)
.
|
. To study the mechanisms underlying the induction of COX-2 by K-Ras, we stably transfected the luciferase reporter gene linked with the COX-2 promoter region into IEC-iK-Ras cells (IEC-iK-Ras/COX-2 5'-Luc). The 5'-flanking region of the human COX-2 gene (nucleotides -1432 to +59) exhibited promoter activity that was increased by induction of oncogenic K-Ras. Treatment with IPTG for 24 h increased COX-2 promoter activity by 70% (Fig. 2B)
.
|
, COX-2 mRNA was rapidly degraded in noninduced IEC-iK-Ras cells (T1/2 30 min). IPTG treatment increased the stability of COX-2 mRNA and extended the T1/2 up to 90 min. We next prepared IEC-iK-Ras cells that contained the CMV promoter-driven luciferase reporter gene linked with 1.4 kb of the COX-2 3' UTR (IEC-iK-Ras/luc+COX-2 3'UTR). Treatment with IPTG for 24 h increased the luciferase activity by >100% in IEC-iK-Ras/luc+COX-2 3'UTR cells, suggesting that oncogenic K-Ras stabilized the 3' UTR of COX-2 mRNA (Fig. 2D)
.
Induction of ERK and Akt/PKB by K-Ras.
Raf/MEK/ERKs represent an important downstream signaling pathway of Ras. As expected, induction of K-Ras increased the levels of activated ERK1/2 (phosphorylated ERK1/2) in IEC-iK-Ras cells (Fig. 3A)
. Kinase activity assays revealed that expression of K-RasVal12 greatly increased the ERK kinase activity (Fig. 3B)
. Akt/PKB can be activated in a Ras-dependent or -independent manner (17)
. To determine whether expression of K-RasVal12 activates Akt/PKB, we first measured the levels of active Akt in Ras-induced IEC-iK-Ras cells. Western blot analysis showed that induction of K-RasVal12 increased the levels of the activated form of Akt/PKB (phosphorylated at serine 473) in IEC-iK-Ras cells (Fig. 3A)
. The expression of oncogenic K-Ras significantly elevated the levels of Akt kinase activity in IEC-iK-Ras cells, as determined by its capability to phosphorylate GSK-3 kinase (Fig. 3C)
.
|
, treatment with IPTG strongly induced the expression of COX-2 in IEC-iK-Ras cells compared with controls. Addition of the selective MEK inhibitor, PD 98059 (50 µM), completely blocked the K-Ras-mediated induction of COX-2, whereas addition of the selective PI3K inhibitor, LY 294002 (20 µM), partially inhibited K-Ras-mediated COX-2 induction. To determine the interaction between the Raf/MEK/ERK and PI3K/Akt/PKB pathways, K-RasVal12 was induced in the presence of PD 98059 or LY 294002. IPTG treatment for 24 h increased the levels of active pERK1/2, pAkt, and COX-2 (Fig. 4B)
. Addition of PD 98059 abolished the Ras-mediated induction of pERK1/2 and blocked induction of pAkt and COX-2, whereas LY 294002 blocked the elevation of pAkt and partially inhibited the induction of COX-2 but did not affect the levels of active pERK1/2. A specific inhibitor of the epidermal growth factor receptor signal transduction pathway, AG1478 (25 µM), did not alter the levels of K-Ras-induced pERK1/2, pAkt, or COX-2.
|
. In agreement with the effect of LY 294002 on COX-2 expression, ectopic expression of Akt-K179M significantly (but incompletely) blocked the K-Ras-mediated induction of COX-2 (Fig. 5B)
.
|
, oncogenic K-Ras regulates the expression of COX-2 at both transcriptional and posttranscriptional levels. It was of interest to determine the signaling pathway(s) responsible for the regulation of COX-2 expression at both levels. IEC-iK-Ras/COX-2 5'-Luc and IEC-iK-Ras/luc-COX-2 3' UTR cells were treated with IPTG in the presence or absence of PD 98059 (50 µM). Luciferase assays of extracts from these cells revealed that PD 98059 almost completely blocked the K-Ras-induced transcription of COX-2 (Fig. 6A)
and K-Ras-mediated stabilization of COX-2 mRNA (Fig. 6B)
, indicating that MEK/ERK activity is required for both transcriptional and posttranscriptional modulation of COX-2 expression.
|
, expression of active Akt-myr or dominant negative Akt-K179M did not significantly alter the activity of the COX-2 promoter in both Ras-induced and uninduced IEC-iK-Ras cells. However, expression of Akt-K179M reduced the stability of the COX-2 3' UTR by 35% in uninduced IEC-iK-Ras cells and blocked the K-Ras-induced stabilization of COX-2 3' UTR. Ectopic expression of constitutively active Akt-myr increased the stability of the COX-2 3' UTR by 110%, so that the induction of K-RasVal12 only slightly increased the stability of COX-2 3' UTR.
|
, expression of the dominant negative regulatory subunit of PI3K (p85) did not alter the K-Ras-induced activity of the COX-2 promoter (Fig. 7C)
but completely inhibited the K-Ras-mediated stabilization of the COX-2 3' UTR (Fig. 7D)
. |
DISCUSSION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
It is well documented that both Ras/Rac1/MEKK1/JNK and Ras/Raf-1/MEK/ERK signal transduction pathways are necessary for the transcriptional induction of COX-2. Ras activates the MEKK1/JNKK/JNK kinase cascade (4 , 32) , leading to phosphorylation of c-Jun, which results in transcriptional activation of COX-2 via the cyclic AMP response element (CRE; 33 , 34 ). Inhibition of MEK/ERK activity leads to a reduction in COX-2 transcription (33) . Subbaramaiah et al. (35) reported that inhibition of MEK, JNK, and p38 MAPK blocked the induction of COX-2 by ceramide and that phosphorylation of c-Jun and transactivation via the CRE cis element in the COX-2 promoter is required for the induction of COX-2 by ceramide. The CCAAT/enhancer-binding protein ß (C/EBP ß) is thought to be required for COX-2 induction via the Raf/MEK/ERK pathway (34) . Our results show that MEK/ERK activity is essential for the K-Ras-mediated induction of COX-2 and that treatment with PD 98059 blocks K-Ras-induced transcriptional activation of the COX-2 promoter.
Cumulative evidence indicates that the expression of COX-2 is also regulated at the posttranscriptional level (36) . We recently reported that the induction of COX-2 in conditionally Ha-RasVal12 transformed Rat-1 cells occurs via a modest increase in COX-2 transcription with a significant increase in the stability of COX-2 mRNA (11) . Induction of oncogenic Ras stabilizes the 3' UTR of COX-2 mRNA in intestinal epithelial cells. A conserved A-U rich region (ARE) is responsible for the rapid turnover of COX-2 mRNA (30) and for the stabilization of COX-2 mRNA by Ras (10) . Consistent with these findings, expression of oncogenic K-Ras increased both the transcriptional activity of the COX-2 promoter and the stability of COX-2 mRNA in IEC cells.
Our results provide evidence that Akt/PKB activity plays an important role in K-Ras-induced expression of COX-2. Treatment with LY 294002 partially blocks the induction of COX-2 by oncogenic K-Ras. Expressing a dominant negative mutant of Akt (Akt-K179M) significantly blocked the K-Ras-induced elevation of COX-2 expression, suggesting that Akt activity is required for the maximal induction of COX-2 by K-Ras. The results from transient transfection experiments clearly show that regulation of COX-2 expression by Akt/PKB occurs predominantly by modulation of the stability of COX-2 mRNA. Expression of Akt-K179M reduced the stability of COX-2 3' UTR and blocked the Ras-induced stabilization of COX-2 3' UTR, whereas expression of active Akt-myr greatly increased the stability of COX-2 3' UTR. Further induction of K-RasVal12 only exerted a limited effect on the stability of the COX-2 3' UTR. These findings are strongly supported by the results obtained from transfection studies using a dominant negative PI3K construct. Inhibition of PI3K activity also blocked the K-Ras-induced stabilization of COX-2 3' UTR but does not affect the transcription of COX-2, confirming the importance of the PI3K/Akt/PKB pathway for the regulation of COX-2 mRNA stability.
In summary, COX-2 is a K-Ras targeted gene and is up-regulated by the induction of oncogenic K-Ras. Expression of mutated K-Ras activates the Rac1/MEKK1/JNK and Raf/MEK/ERK pathways that result in increased transcription of COX-2. Oncogenic K-Ras also activates the PI3K/Akt/PKB pathway, which cooperates with the MEK/ERK pathway and results in posttranscriptional stabilization of COX-2 mRNA (Fig. 8)
. Given the important roles of both COX-2 and Akt in carcinogenesis, our results suggest that COX-2 is regulated by PI3K/Akt/PKB and may contribute to the neoplastic potential of the PI3K/Akt/PKB pathway.
|
|
FOOTNOTES |
|---|
1 Supported by NIH Grants DK-47297, CA-77839 (to R. N. D.), and CA-68485 (Vanderbilt-Ingram Cancer Center) and a Veterans Affairs Merit Grant. 
2 To whom requests for reprints should be addressed, at Department of Medicine/GI; MCN C-2104, Vanderbilt University Medical Center, 1161 21st Avenue South, Nashville, TN 27232-2279. Phone: (615) 343-5200; Fax: (615) 343-6229; E-mail: raymond.dubois{at}mcmail.vanderbilt.edu
3 The abbreviations used are: MEK, MAPK/ERK kinase; MAPK, mitogen-activated protein kinase; ERK, extracellular signal-regulated kinase; PI3K, phosphatidylinositol 3-kinase; Akt/PKB, protein kinase B; COX, cyclooxygenase; IPTG, isopropyl-1-thio-ß-D-galactopyranoside; DRB, 5,6-dichlorobenzimidazole riboside; 3' UTR, 3' untranslated region; PI3K, phosphatidylinositol 3-kinase; CMV, cytomegalovirus; IEC, intestinal epithelial cell; HA, hyaluronic acid.
Received 7/ 6/00. Accepted 1/17/01.
|
REFERENCES |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
B by the Akt/PKB kinase. Curr. Biol., 9: 601-604, 1999.[Medline]
This article has been cited by other articles:
|
|
 |
|
  U. Dougherty, D. Cerasi, I. Taylor, M. Kocherginsky, U. Tekin, S. Badal, L. Aluri, A. Sehdev, S. Cerda, R. Mustafi, et al. Epidermal Growth Factor Receptor Is Required for Colonic Tumor Promotion by Dietary Fat in the Azoxymethane/Dextran Sulfate Sodium Model: Roles of Transforming Growth Factor-{alpha} and PTGS2 Clin. Cancer Res., November 15, 2009; 15(22): 6780 - 6789. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Shao, M.K. Washington, R. Saxena, and H. Sheng Heterozygous disruption of the PTEN promotes intestinal neoplasia in APCmin/+ mouse: roles of osteopontin Carcinogenesis, December 1, 2007; 28(12): 2476 - 2483. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Mizukami, Y. Kohgo, and D. C. Chung Hypoxia Inducible Factor-1 Independent Pathways in Tumor Angiogenesis Clin. Cancer Res., October 1, 2007; 13(19): 5670 - 5674. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Klampfer, J. Huang, S. Shirasawa, T. Sasazuki, and L. Augenlicht Histone Deacetylase Inhibitors Induce Cell Death Selectively in Cells That Harbor Activated kRasV12: The Role of Signal Transducers and Activators of Transcription 1 and p21 Cancer Res., September 15, 2007; 67(18): 8477 - 8485. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. C. Azim, H. Cao, X. Gao, M. Joo, A. B. Malik, R. B. van Breemen, R. T. Sadikot, G. Park, and J. W. Christman Regulation of cyclooxygenase-2 expression by small GTPase Rac2 in bone marrow macrophages Am J Physiol Lung Cell Mol Physiol, September 1, 2007; 293(3): L668 - L673. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Koyama, Y. Matsuzaki, S. Yogosawa, T. Hitomi, M. Kawanaka, and T. Sakai ZD1839 induces p15INK4b and causes G1 arrest by inhibiting the mitogen-activated protein kinase/extracellular signal-regulated kinase pathway Mol. Cancer Ther., May 1, 2007; 6(5): 1579 - 1587. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Stempelj, M. Kedinger, L. Augenlicht, and L. Klampfer Essential Role of the JAK/STAT1 Signaling Pathway in the Expression of Inducible Nitric-oxide Synthase in Intestinal Epithelial Cells and Its Regulation by Butyrate J. Biol. Chem., March 30, 2007; 282(13): 9797 - 9804. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Gervais, C. Dugourd, L. Muller, C. Ardidie, B. Canton, L. Loviconi, P. Corvol, H. Chneiweiss, and C. Monnot Akt Down-Regulates ERK1/2 Nuclear Localization and Angiotensin II-induced Cell Proliferation through PEA-15 Mol. Biol. Cell, September 1, 2006; 17(9): 3940 - 3951. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Upadhyay, C. Liu, A. Chatterjee, M. O. Hoque, M. S. Kim, J. Engles, W. Westra, B. Trink, E. Ratovitski, and D. Sidransky LKB1/STK11 Suppresses Cyclooxygenase-2 Induction and Cellular Invasion through PEA3 in Lung Cancer Cancer Res., August 15, 2006; 66(16): 7870 - 7879. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 W.-C. Tsai, S.-T. Tsai, Y.-T. Jin, and L.-W. Wu Cyclooxygenase-2 Is Involved in S100A2-Mediated Tumor Suppression in Squamous Cell Carcinoma Mol. Cancer Res., August 1, 2006; 4(8): 539 - 547. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Hoang, L. Zhu, Y. Shi, P. Frost, H. Yan, S. Sharma, S. Sharma, L. Goodglick, S. Dubinett, and A. Lichtenstein Oncogenic RAS mutations in myeloma cells selectively induce cox-2 expression, which participates in enhanced adhesion to fibronectin and chemoresistance Blood, June 1, 2006; 107(11): 4484 - 4490. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Thiel, M. Heinonen, J. Rintahaka, T. Hallikainen, A. Hemmes, D. A. Dixon, C. Haglund, and A. Ristimaki Expression of Cyclooxygenase-2 Is Regulated by Glycogen Synthase Kinase-3beta in Gastric Cancer Cells J. Biol. Chem., February 24, 2006; 281(8): 4564 - 4569. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. G. Banerjee, I. Bhattacharyya, and J. K. Vishwanatha Identification of genes and molecular pathways involved in the progression of premalignant oral epithelia Mol. Cancer Ther., June 1, 2005; 4(6): 865 - 875. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Daikoku, D. Wang, S. Tranguch, J. D. Morrow, S. Orsulic, R. N. DuBois, and S. K. Dey Cyclooxygenase-1 Is a Potential Target for Prevention and Treatment of Ovarian Epithelial Cancer Cancer Res., May 1, 2005; 65(9): 3735 - 3744. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Symowicz, B. P. Adley, M. M.M. Woo, N. Auersperg, L. G. Hudson, and M. S. Stack Cyclooxygenase-2 Functions as a Downstream Mediator of Lysophosphatidic Acid to Promote Aggressive Behavior in Ovarian Carcinoma Cells Cancer Res., March 15, 2005; 65(6): 2234 - 2242. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. L. Sheu, F. M. Ho, R. S. Yang, K. F. Chao, W. W. Lin, S. Y. Lin-Shiau, and S.-H. Liu High Glucose Induces Human Endothelial Cell Apoptosis Through a Phosphoinositide 3-Kinase-Regulated Cyclooxygenase-2 Pathway Arterioscler Thromb Vasc Biol, March 1, 2005; 25(3): 539 - 545. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. W. Slice, T. Chiu, and E. Rozengurt Angiotensin II and Epidermal Growth Factor Induce Cyclooxygenase-2 Expression in Intestinal Epithelial Cells through Small GTPases Using Distinct Signaling Pathways J. Biol. Chem., January 14, 2005; 280(2): 1582 - 1593. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C.-H. Chou, L.-H. Wei, M.-L. Kuo, Y.-J. Huang, K.-P. Lai, C.-A. Chen, and C.-Y. Hsieh Up-regulation of interleukin-6 in human ovarian cancer cell via a Gi/PI3K-Akt/NF-{kappa}B pathway by lysophosphatidic acid, an ovarian cancer-activating factor Carcinogenesis, January 1, 2005; 26(1): 45 - 52. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Maciag, G. Sithanandam, and L. M. Anderson Mutant K-rasV12 increases COX-2, peroxides and DNA damage in lung cells Carcinogenesis, November 1, 2004; 25(11): 2231 - 2237. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B.-C. Chen, C.-C. Yu, H.-C. Lei, M.-S. Chang, M.-J. Hsu, C.-L. Huang, M.-C. Chen, J.-R. Sheu, T.-F. Chen, T.-L. Chen, et al. Bradykinin B2 Receptor Mediates NF-{kappa}B Activation and Cyclooxygenase-2 Expression via the Ras/Raf-1/ERK Pathway in Human Airway Epithelial Cells J. Immunol., October 15, 2004; 173(8): 5219 - 5228. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M.-S. Chang, W.-S. Lee, B.-C. Chen, J.-R. Sheu, and C.-H. Lin YC-1-Induced Cyclooxygenase-2 Expression Is Mediated by cGMP-Dependent Activations of Ras, Phosphoinositide-3-OH-kinase, Akt, and Nuclear Factor-{kappa}B in Human Pulmonary Epithelial Cells Mol. Pharmacol., September 1, 2004; 66(3): 561 - 571. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B.-C. Chen, Y.-S. Chang, J.-C. Kang, M.-J. Hsu, J.-R. Sheu, T.-L. Chen, C.-M. Teng, and C.-H. Lin Peptidoglycan Induces Nuclear Factor-{kappa}B Activation and Cyclooxygenase-2 Expression via Ras, Raf-1, and ERK in RAW 264.7 Macrophages J. Biol. Chem., May 14, 2004; 279(20): 20889 - 20897. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. D. WARNER and J. A. MITCHELL Cyclooxygenases: new forms, new inhibitors, and lessons from the clinic FASEB J, May 1, 2004; 18(7): 790 - 804. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Shao, B. M. Evers, and H. Sheng Prostaglandin E2 Synergistically Enhances Receptor Tyrosine Kinase-dependent Signaling System in Colon Cancer Cells J. Biol. Chem., April 2, 2004; 279(14): 14287 - 14293. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Du, B. Jiang, R. J. Coffey, and J. Barnard Raf and RhoA Cooperate to Transform Intestinal Epithelial Cells and Induce Growth Resistance to Transforming Growth Factor {beta} Mol. Cancer Res., April 1, 2004; 2(4): 233 - 241. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H.-Y. Lee, Y.-A. Suh, J. W. Kosmeder, J. M. Pezzuto, W. K. Hong, and J. M. Kurie Deguelin-Induced Inhibition of Cyclooxygenase-2 Expression in Human Bronchial Epithelial Cells Clin. Cancer Res., February 1, 2004; 10(3): 1074 - 1079. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Shao, B. M. Evers, and H. Sheng Roles of Phosphatidylinositol 3'-Kinase and Mammalian Target of Rapamycin/p70 Ribosomal Protein S6 Kinase in K-Ras-Mediated Transformation of Intestinal Epithelial Cells Cancer Res., January 1, 2004; 64(1): 229 - 235. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
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]
|
|
|
|
 |
|
 H Sheng, J Shao, C M Townsend jr, and B M Evers Phosphatidylinositol 3-kinase mediates proliferative signals in intestinal epithelial cells Gut, October 1, 2003; 52(10): 1472 - 1478. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Khare, S. Cerda, R. K. Wali, F. C. von Lintig, M. Tretiakova, L. Joseph, D. Stoiber, G. Cohen, K. Nimmagadda, J. Hart, et al. Ursodeoxycholic Acid Inhibits Ras Mutations, Wild-type Ras Activation, and Cyclooxygenase-2 Expression in Colon Cancer Cancer Res., July 1, 2003; 63(13): 3517 - 3523. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. A. Benitah, P. F. Valeron, and J. C. Lacal ROCK and Nuclear Factor-{kappa}B-dependent Activation of Cyclooxygenase-2 by Rho GTPases: Effects on Tumor Growth and Therapeutic Consequences Mol. Biol. Cell, July 1, 2003; 14(7): 3041 - 3054. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Sengupta, B.-C. Jang, M.-T. Wu, J.-H. Paik, H. Furneaux, and T. Hla The RNA-binding Protein HuR Regulates the Expression of Cyclooxygenase-2 J. Biol. Chem., June 27, 2003; 278(27): 25227 - 25233. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Tiwari, H. Sakaue, J. R. Pollack, and R. A. Roth Gene Expression Profiling in Prostate Cancer Cells With Akt Activation Reveals Fra-1 As an Akt-Inducible Gene Mol. Cancer Res., April 1, 2003; 1(6): 475 - 484. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Liang, W. Jin, C. Knuefermann, M. Schmidt, G. B. Mills, K. K. Ang, L. Milas, and Z. Fan Targeting the Phosphatidylinositol 3-Kinase/Akt Pathway for Enhancing Breast Cancer Cells to Radiotherapy Mol. Cancer Ther., April 1, 2003; 2(4): 353 - 360. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Heuze-Vourc'h, L. Zhu, K. Krysan, R. K. Batra, S. Sharma, and S. M. Dubinett Abnormal Interleukin 10R{alpha} Expression Contributes to the Maintenance of Elevated Cyclooxygenase-2 in Non-Small Cell Lung Cancer Cells Cancer Res., February 15, 2003; 63(4): 766 - 770. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. L. Rice, M. Washington, S. Schleman, K. S. Beard, L. J. Driggers, and D. J. Ahnen Sulindac Sulfide Inhibits Epidermal Growth Factor-induced Phosphorylation of Extracellular-regulated Kinase 1/2 and Bad in Human Colon Cancer Cells Cancer Res., February 1, 2003; 63(3): 616 - 620. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Araki, S. Okamura, S. P. Hussain, M. Nagashima, P. He, M. Shiseki, K. Miura, and C. C. Harris Regulation of Cyclooxygenase-2 Expression by the Wnt and Ras Pathways Cancer Res., February 1, 2003; 63(3): 728 - 734. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Dong, K. Guda, P. R. Nambiar, A. Rezaie, G. S. Belinsky, G. Lambeau, C. Giardina, and D. W. Rosenberg Inverse association between phospholipase A2 and COX-2 expression during mouse colon tumorigenesis Carcinogenesis, February 1, 2003; 24(2): 307 - 315. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Moon and J. J. Pestka Vomitoxin-Induced Cyclooxygenase-2 Gene Expression in Macrophages Mediated by Activation of ERK and p38 but Not JNK Mitogen-Activated Protein Kinases Toxicol. Sci., October 1, 2002; 69(2): 373 - 382. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. M. Monick, P. K. Robeff, N. S. Butler, D. M. Flaherty, A. B. Carter, M. W. Peterson, and G. W. Hunninghake Phosphatidylinositol 3-Kinase Activity Negatively Regulates Stability of Cyclooxygenase 2 mRNA J. Biol. Chem., August 30, 2002; 277(36): 32992 - 33000. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Ferrandina, L. Lauriola, G. F. Zannoni, A. Fagotti, F. Fanfani, F. Legge, N. Maggiano, M. Gessi, S. Mancuso, F. O. Ranelletti, et al. Increased cyclooxygenase-2 (COX-2) expression is associated with chemotherapy resistance and outcome in ovarian cancer patients Ann. Onc., August 1, 2002; 13(8): 1205 - 1211. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Shao, H. Sheng, and R. N. DuBois Peroxisome Proliferator-activated Receptors Modulate K-Ras-mediated Transformation of Intestinal Epithelial Cells Cancer Res., June 1, 2002; 62(11): 3282 - 3288. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Ferrandina, L. Lauriola, M. G. Distefano, G. F. Zannoni, M. Gessi, F. Legge, N. Maggiano, S. Mancuso, A. Capelli, G. Scambia, et al. Increased Cyclooxygenase-2 Expression Is Associated With Chemotherapy Resistance and Poor Survival in Cervical Cancer Patients J. Clin. Oncol., February 15, 2002; 20(4): 973 - 981. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Cancer Research | Clinical Cancer Research |
| Cancer Epidemiology Biomarkers & Prevention | Molecular Cancer Therapeutics |
| Molecular Cancer Research | Cancer Prevention Research |
| Cancer Prevention Journals Portal | Cancer Reviews Online |
| Annual Meeting Education Book | Meeting Abstracts Online |
