POU5F1 and esophageal squamous cell carcinoma: Shahryari et al. demonstrated that, in esophageal squamous cell carcinoma, two novel splice variants of SOX2OT: SOX2OT-S1 and SOX2OT-S2, are co-upregulated with SOX2 and OCT4, and suggested that SOX2OT splice variants partly participate in tumor initiation and/or progression [44].