CNTN1 and lung cancer: Contactin 1 (CNTN1), a neuronal membrane glycoprotein, has long been implicated in cancer cell invasion, migration, metastasis via the epithelial-mesenchymal transition (EMT) in several cancers such as the lung cancer, gastric cancer, esophageal cancer, thyroid cancer, liver cancer, prostate cancer, and breast cancer (86–93).