Current study revealed that the knockdown of SerpinB2 in tumor cells led to a notable decrease in the sphere formation and migration of MDA-MB-231 cells and delayed mammary cancer progression and LN metastasis in PyMTSB2−/− mice, suggesting that mammary tumor cell-produced SerpinB2 may contribute to the aggressiveness on of mammary tumor cells. Here, SERPINB2 is linked to breast cancer.