Type

Other / n/a

Authors

Desmond J Fitzgerald
Frank E Murray
Elaine Kay
Sandra C Austin
Vikrum Malhotra
Eamonn S Molloy
Sinead M Byrne
Glen A Doherty

Subjects

Biochemistry

Topics
colorectal cancer crc tyrosine kinase inhibitor cancer receptors cell surface colorectal cell cycle arrest life sciences cox 2 inhibitor

Proneoplastic effects of PGE2 mediated by EP4 receptor in colorectal cancer. (2009)

Abstract BACKGROUND: Prostaglandin E2 (PGE2) is the major product of Cyclooxygenase-2 (COX-2) in colorectal cancer (CRC). We aimed to assess PGE2 cell surface receptors (EP 1-4) to examine the mechanisms by which PGE2 regulates tumour progression. METHODS: Gene expression studies were performed by quantitative RT-PCR. Cell cycle was analysed by flow cytometry with cell proliferation quantified by BrdU incorporation measured by enzyme immunoassay. Immunohistochemistry was employed for expression studies on formalin fixed paraffin embedded tumour tissue. RESULTS: EP4 was the most abundant subtype of PGE2 receptor in HT-29 and HCA7 cells (which show COX-2 dependent PGE2 generation) and was consistently the most abundant transcript in human colorectal tumours (n = 8) by qRT-PCR (ANOVA, p = 0.01). G0/G1 cell cycle arrest was observed in HT-29 cells treated with SC-236 5 microM (selective COX-2 inhibitor) for 24 hours (p = 0.02), an effect abrogated by co-incubation with PGE2 (1 microM). G0/G1 arrest was also seen with a specific EP4 receptor antagonist (EP4A, L-161982) (p = 0.01). Treatment of HT-29 cells with either SC-236 or EP4A caused reduction in intracellular cAMP (ANOVA, p = 0.01). Early induction in p21WAF1/CIP1 expression (by qRT-PCR) was seen with EP4A treatment (mean fold increase 4.4, p = 0.04) while other genes remained unchanged. Similar induction in p21WAF1/CIP1 was also seen with PD153025 (1 microM), an EGFR tyrosine kinase inhibitor, suggesting EGFR transactivation by EP4 as a potential mechanism. Additive inhibition of HCA7 proliferation was observed with the combination of SC-236 and neutralising antibody to amphiregulin (AR), a soluble EGFR ligand. Concordance in COX-2 and AR localisation in human colorectal tumours was noted. CONCLUSION: COX-2 regulates cell cycle transition via EP4 receptor and altered p21WAF1/CIP1 expression. EGFR pathways appear important. Specific targeting of the EP4 receptor or downstream targets may offer a safer alternative to COX-2 inhibition in the chemoprevention of CRC.
Collections Ireland -> Royal College of Surgeons in Ireland -> Department of Molecular and Cellular Therapeutics
Ireland -> Royal College of Surgeons in Ireland -> Molecular and Cellular Therapeutics Articles

Full list of authors on original publication

Desmond J Fitzgerald, Frank E Murray, Elaine Kay, Sandra C Austin, Vikrum Malhotra, Eamonn S Molloy, Sinead M Byrne, Glen A Doherty

Experts in our system

1
D J Fitzgerald
Royal College of Surgeons in Ireland
Total Publications: 101
 
2
F E Murray
Royal College of Surgeons in Ireland
 
3
Elaine W Kay
Royal College of Surgeons in Ireland
Total Publications: 157
 
4
Eamonn S Molloy
Royal College of Surgeons in Ireland
Total Publications: 7
 
5
Glen A Doherty
University College Dublin
Total Publications: 57