The analysis of apoptotic marker proteins with Western blotting showed that the relative expression levels of pro-apoptotic protein Bax and cleaved caspase-3 were significantly increased, and antiapoptotic protein Bcl2 was obviously decreased in E8-PE38-treated HT115 or HCT116 cells, indicating that E8-PE38 immunotoxin can induce the apoptosis of CRC cells in vitro (Fig. 4H and I). This evidence concerns the gene CASP3 and colorectal carcinoma.