Liver kinase B1 (LKB1), also known as serine threonine kinase 11 (STK11), is a tumor suppressor protein originally identified as the causative gene of Peutz-Jeghers syndrome (PJS), which is closely associated with the development of gastrointestinal polyps and cancer [1,2]. The gene discussed is STK11; the disease is Peutz-Jeghers syndrome.