Lindgren et al. reported that elevated blood pressure was associated with increased risk of lung cancer in smoking, hypertensive men,67 but most other cohort studies reported a null effect.68–72 The biological mechanism of such an association has rarely been investigated, but one recent study suggested that angiotensin-converting enzyme inhibitors are linked to a small increase in the risk of lung cancer and could be a potential confounder.73 Further studies are required to clarify this issue. This evidence concerns the gene ACE and lung cancer.