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. Here, CASP3 is linked to esophageal squamous cell carcinoma.