The epithelial cell and lung cancer: the link between chronic obstructive pulmonary disease and lung cancer.

Chronic obstructive pulmonary disease (COPD) and lung cancer currently form the basis for an enormous disease burden in the developed world. As a result of changing smoking trends and tobacco use, regrettably, a similar picture is arising rapidly within the developing world. COPD is a recognised risk factor for lung cancer, and a significant proportion of patients diagnosed with lung cancer have COPD. An association between both conditions has long been suspected but has proven difficult to demonstrate thus far. However, the common factors between both conditions are now becoming apparent thanks to recent clinical and molecular advances. Abnormal regulation of the immune system and the establishment of chronic inflammation appear to be key events in this process. In addition, the complex interplay between genes and environment and the possibility of a genetic basis to lung cancer susceptibility in the context of COPD are becoming clearer concepts. As we begin to unravel the common pathways and molecules in the pathogenesis of both conditions, we may be able to not only identify novel strategies to prevent and treat COPD and lung cancer, but also recognise molecular markers to identify patients at high risk of developing lung cancer.