EN2 and esophageal squamous cell carcinoma: Studies show that EN2 plays an important role in the proliferation, migration, and invasion of various tumor cells, including prostate cancer, colorectal cancer, esophageal squamous cell carcinoma, lung cancer, and bladder cancer, and is closely related to the poor prognosis of tumor patients (Zhou et al., 2017; Lin et al., 2018; Cao et al., 2020; Li et al., 2020; Li et al., 2021).