Since the Expression of p-STAT3 protein as well as its downstream targets might account for 4T1 cells reduction of tumorigenicity, we discovered that the expression of p-STAT3, MMP9, MMP2 and VEGF were related to the migration and invasion of tumor cells; while the expression of caspase3, Bcl-2, PARP were related to tumor cells apoptosis. The gene discussed is MMP9; the disease is neoplasm.