The results demonstrated that 17β‐estradiol treatment inhibit HBMMSCS‐induced cellular motility by suppressing activation and expression of IL‐8‐up‐regulated Src downstream target proteins including phospho‐Cas, phospho‐paxillin, phospho‐ERK1/2, phospho‐JNK1/2, MMP9, tPA and uPA in human gastric cancer cells. This evidence concerns the gene MAPK3 and gastric cancer.