These results indicated that downstream signaling pathway of p53 was functional in GIST 430 cells, as the expression of total MDM2 greatly increased in response to the treatment of SCF-DM1 and DM1, but the ability of p53 to induce apoptosis was impaired in GIST 430 cells when treated by SCF-DM1 and DM1. This evidence concerns the gene KITLG and gastrointestinal stromal tumor.