Cyclooxygenase-2 knockdown by RNA interference in colon cancer.

Abstract

Overexpression of cyclooxygenase-2 (COX-2) is observed early in colon cancer. Treatments with COX-2-specific NSAIDs have been shown to reduce polyp size and polyp number in FAP patients with a predisposition to colorectal adenoma and cancer. However, the use of COX-2-specific NSAIDs in colon cancer patients has recently revealed increased cardiovascular risks. These harmful side effects may be the result of COX-dependent and/or COX-independent mechanisms. RNA interference (RNAi) is a method of post-transcriptional gene silencing intrinsic to cells. This study employed RNAi to specifically knockdown endogenous COX-2 expression in the HT-29 colon cancer cell line, and to observe the apoptotic response as well as 15-hydroxyprostaglandin dehydrogenase (15-PGDH) expression levels. Following treatment with a COX-2 siRNA, we demonstrated a significant knockdown at the protein level of 57% as compared to a non-silencing siRNA control. Protein results were corroborated by concurrent decrease in COX-2 mRNA levels following the same treatment regimen. Despite previous studies using NSAID treatment to implicate COX-2 involvement in apoptosis, we did not observe any alteration in Bcl-2 expression and Caspase-3 activation following COX-2 knockdown in these cells. 15-PGDH, a physiological antagonist of COX-2 in its catabolism of PGE2, showed a modest but significant induction in response to COX-2 knockdown. The precise role of COX-2 in apoptosis and PGE2 regulation remains unclear; however, having shown that down-regulation of endogenous levels of COX-2 can be achieved in colon cancer by RNAi, this strategy should prove to be a valuable tool in revealing the specific function of COX-2 in tumourigenesis.

• Authors: George S Charames, Bharati Bapat
• Journal: International journal of oncology (Int J Oncol) Vol. 28 Issue 2 Pg. 543-9 (Feb 2006) ISSN: 1019-6439 [Print] Greece
• PMID: 16391811 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• RNA, Messenger
• RNA, Small Interfering
• Hydroxyprostaglandin Dehydrogenases
• 15-hydroxyprostaglandin dehydrogenase
• Cyclooxygenase 2

Topics

• Colonic Neoplasms
• Cyclooxygenase 2 (genetics, metabolism)
• Gene Silencing
• HT29 Cells
• Humans
• Hydroxyprostaglandin Dehydrogenases (genetics, metabolism)
• RNA Interference
• RNA, Messenger (metabolism)
• RNA, Small Interfering (genetics)
• Transfection