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COX-2 inhibition in clinical cancer prevention
1Department of Gastrointestinal Medicine and Nutrition, University of Texas, M. D. Anderson Cancer Center, Houston, Texas, USA. plynch@mdanderson.org
Abstract:
Colorectal cancer is an excellent model for studying cancer prevention by means of secondary (e.g., polypectomy to remove a precursor adenoma) and primary (chemoprevention) strategies. Evidence has shown that regular users of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) have a reduction in risk of colorectal cancer. A possible mechanism of this benefit is decreased prostaglandin production, which is achieved through inhibition of cyclooxygenase (COX) activity, and possibly other pathways. Two isoforms of COX--COX-1 and COX-2--have been identified. COX-2 is expressed in colorectal adenomas and carcinomas, both in humans and rodents. Inhibition of COX-2 has been shown to decrease the incidence of carcinogen-induced neoplasia in rats and to lower the incidence of adenomas in murine models. Several COX-2 inhibitors, with the potential for less toxicity than that associated with traditional NSAIDs, are under development. This paper reviews potential chemoprevention of colorectal cancer using COX-2 inhibitors in patients at increased risk, e.g., patients with familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, and sporadic adenomas. Included are the rationale for use of such agents, results of a study showing a significant reduction in adenoma burden in familial adenomatous polyposis patients who received the selective COX-2 inhibitor celecoxib (Celebrex), and the design of other ongoing or planned clinical trials.
Insights
Selective cyclooxygenase-2 (COX-2) inhibitors show promise for colorectal cancer prevention. Studies indicate these drugs significantly reduce adenoma burden in high-risk patients, offering a potential new chemoprevention strategy.
Area of Science:
- Oncology
- Gastroenterology
- Pharmacology
Background:
- Colorectal cancer prevention utilizes secondary (polypectomy) and primary (chemoprevention) strategies.
- Regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) is linked to reduced colorectal cancer risk, potentially via prostaglandin reduction through cyclooxygenase (COX) inhibition.
- COX-2 is expressed in colorectal tumors, suggesting it as a therapeutic target.
Purpose of the Study:
- To review the potential of cyclooxygenase-2 (COX-2) inhibitors for colorectal cancer chemoprevention.
- To discuss the rationale, existing evidence, and ongoing clinical trials for COX-2 inhibitors in high-risk populations.
Main Methods:
- Review of existing literature on NSAIDs, COX inhibition, and colorectal cancer.
- Analysis of studies investigating COX-2 inhibitors in preclinical models and human patients.
- Examination of clinical trial designs for COX-2 inhibitors in colorectal cancer prevention.
Main Results:
- Inhibition of COX-2 decreases carcinogen-induced neoplasia in rats and adenoma incidence in murine models.
- A study demonstrated a significant reduction in adenoma burden in familial adenomatous polyposis patients treated with celecoxib (a selective COX-2 inhibitor).
- Several COX-2 inhibitors are in development, potentially offering improved safety profiles compared to traditional NSAIDs.
Conclusions:
- Selective COX-2 inhibitors represent a promising approach for colorectal cancer chemoprevention, particularly in high-risk individuals.
- Further clinical trials are necessary to establish the efficacy and safety of these agents in diverse patient populations.
- COX-2 inhibition offers a targeted strategy for colorectal cancer prevention by targeting a key enzyme in tumor development.