CASP8 and esophageal squamous cell carcinoma: We then measured apoptosis-associated proteins in ESCC cells and found that cotreating cells with SP2509 and UNC0642 group increased cleaved caspase-3, cleaved caspase-8, and cleaved PARP protein levels and decreased XIAP protein levels (Figures 5(e) and 5(f)), supporting the notion that simultaneously inhibiting LSD1 and G9a induces apoptosis in ESCC cells.