CASP6 and gastric cancer: The mechanism of this synergism by EGFR inhibitors might be responsible for the upregulation of caspase-6, p53, and DAPK-2 and the downregulation of ABCG2 and UGT1A1 in SN38-resistant gastric cancer cells, resulting in the induction of apoptosis of irinotecan-resistant cells.