SOX2 and neoplasm: The proliferation-inhibitory phenotype observed in KYSE140 cells was rescued by ectopically expressing SOX2 (Supplementary Fig. 4b), indicating that e1 regulates cell proliferation through activating SOX2. We also transplanted the LK2 cells with and without e1 repression into flanks of nude mice, which showed that activity of the e1 enhancer is required for in vivo tumor growth (Fig. 3e).