Barrett's to oesophageal cancer sequence: a model of inflammatory-driven upper gastrointestinal cancer

Cancer-related inflammation is considered the 'seventh hallmark of cancer'; many studies show that tumours develop and progress within inflammatory diseases. This review focuses on Barrett's oesophagus, a common condition in which chronic inflammation and resulting alterations in the stroma can lead to carcinogenesis, specifically oesophageal adenocarcinoma. Changes that occur in the tissue microenvironment during development of this disease are discussed. Infiltration of immune cells facilitates tumour development through production of factors that promote carcinogenesis and by enabling tumours to evade the host immune response. Small molecules including cytokines, chemokines and growth factors play key roles in both inflammation and cancer by promoting proliferation, angiogenesis and carcinogenesis and by recruiting immune cells. The extracellular matrix is altered in inflammation, and provides structural support to developing tumours. Hypoxia is a common state in cancers and inflamed tissues which causes DNA damage and induces tumourigenic factors. Finally, tissue vasculature is a vital part of its microenvironment, supplying oxygen, nutrients and growth factors to rapidly dividing cells, and providing a mechanism for metastatic spread. The cells and molecules outlined here represent potential targets for treatment of this cancer, especially in its pre-cancerous, inflammatory stage.