Chronic inflammation and pathogenesis of GI and pancreatic cancers

The pathogenesis of cancer represents a complex and multifactorial process requiring a number of acquired and genetic defects. It is becoming increasingly apparent that many cancers originate from a chronic inflammatory process. The topic of this review is the inflammatory response and development of gastrointestinal (GI) and pancreatic cancers. Here, we describe the development of various gastric colorectal and pancreatic cancers through an inflammatory process. The tumor microenvironment which predisposes to tissue destruction, subsequent attempts at healing and accumulation of cellular damage with loss of cell cycle control mechanisms is discussed. Components of the tumor microenvironment that are important in the final common pathway leading to cancer include the tumor stroma, tumor-associated macrophages, cytokines and chemokines and reactive oxygen and nitrogen species. Common signaling pathways that link inflammation with cancer are described and include the COX-2, NF-kappaB and phosphatidyl inositol 3-kinase (PI3K) pathways. Finally, therapies that can be directed to the inflammatory process as either treatment or prevention of these cancers will be discussed including novel inhibitors of signaling pathways which are currently in development.