Since it is technically difficult to analyze the treatment effect on the apoptosis level of only the Panc1 cells in the heterospheroids, we used the M30 Apoptosense® CK18 kit, which detects the epithelial-specific soluble caspase-cleaved cytokeratin 18 (ccK18), to determine apoptosis specifically in the cancer cells. Here, KRT18 is linked to cancer.