Back to the future: COX-2 inhibitors for chemoprevention and cancer therapy

For more than a century, inhibition of prostaglandin biosynthesis via inhibition of the fatty acid cyclooxygenase (COX) has been achieved by non-steroidal anti-inflammatory drugs (NSAIDs), which targets both COX-1 and COX-2 and as such could be responsible for causing gastrointestinal (GI) toxicity. COX-2 is an inducible enzyme produced by many cell types in response to multiple stimuli. Recently, COX-2 over-expression has been found in several types of human cancers such as colon, breast, prostate and pancreas and appears to control many cellular processes. Because of its role in carcinogenesis, apoptosis, and angiogenesis, it is an excellent target for developing new drugs with selectivity for prevention and/or treatment of human cancers. Development of selective COX-2 inhibitors has been successfully documented and as such showed less toxicity to GI tract as compared to conventional NSAIDs. However, the long term use of COX-2 selective inhibitors showed cardiovascular toxicity, and thus their utilization for cancer prevention and therapy is currently questionable, suggesting that further development of novel COX-2 selective agents are needed. Among many solid tumors, pancreatic cancer has the worst prognosis, and inflammation has been identified as a significant factor in the development of pancreatic malignancy. Several cytokines, reactive oxygen species (ROS) and mediators of inflammatory pathway such as activation of nuclear factor-kappaB (NF-kappaB) and COX-2 leads to an increase in cell proliferation, survival, and inhibition of pro-apoptotic pathway, ultimately resulting in tumor angiogenesis, invasion and metastasis. In this brief review, we summarize the role of COX-2 and discuss some of the experimental data linking inflammation with the development of pancreatic cancer. In addition, we provide further evidence regarding the state of our knowledge toward the development of novel COX-2 targeting agents for the prevention and/or treatment of human cancers especially pancreatic cancer.