Proneoplastic effects of PGE2 mediated by EP4 receptor in colorectal cancer

<p>Abstract</p> <p>Background</p> <p>Prostaglandin E₂(PGE₂) is the major product of Cyclooxygenase-2 (COX-2) in colorectal cancer (CRC). We aimed to assess PGE₂cell surface receptors (EP 1–4) to examine the mechanisms by which PGE₂regulates tumour progression.</p> <p>Methods</p> <p>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.</p> <p>Results</p> <p>EP4 was the most abundant subtype of PGE₂receptor in HT-29 and HCA7 cells (which show COX-2 dependent PGE₂generation) 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 μM (selective COX-2 inhibitor) for 24 hours (p = 0.02), an effect abrogated by co-incubation with PGE₂(1 μM). 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 p21^WAF1/CIP1expression (by qRT-PCR) was seen with EP4A treatment (mean fold increase 4.4, p = 0.04) while other genes remained unchanged. Similar induction in p21^WAF1/CIP1was also seen with PD153025 (1 μM), 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.</p> <p>Conclusion</p> <p>COX-2 regulates cell cycle transition via EP4 receptor and altered p21^WAF1/CIP1expression. 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.</p

Inhibition of cyclooxygenase -2 and amphiregulin reduces cell proliferation in a colorectal cancer cell line

Background: The role of cyclooxygenase-2 (COX-2) overexpression in colorectal cancers has engaged interest in the role of COX-2 and prostaglandin E2 (PGE2) in cancer cell mitogenesis. Amphiregulin (AR), an epidermal growth factor receptor (EGFR) ligand, has been directly related to PGE2, which activates the AR promoter, causing increased AR expression. Aims: To identify if COX-2 and AR play a role in human colon cancer cell mitogenesis. Methods: HCA-7 cells in culture were treated alone or in combination with an amphiregulin neutralising antibody (ARNA) and a selective COX-2 inhibitor (SC236). The mitogenic effects were assessed by enzyme immunoassay to quantify bromodeoxyuridine (BrdU) incorporation. Results: ARNA (P Conclusions: Novel therapeutic strategies should combine elements that target both pathways.</p

Infectious mononucleosis with secondary cold agglutinin disease causing autoimmune haemolytic anaemia

This case report describes a 20-year-old woman whose initial clinical, laboratory, and radiological presentation suggested obstructive jaundice. However, she was subsequently found to be suffering from autoimmune haemolytic anaemia resulting from an Epstein–Barr virus infection complicated by cold agglutinin disease. The patient went on to make a complete clinical recovery after discharge