ESR1 and breast carcinoma: To determine whether TPX2 contributed to the DMFS discriminatory capacity of this network shRNA knockdown of Tpx2 was performed in a highly metastatic mouse mammary cell line, 6DT1 [13] originally derived from an MMTV-myc transgenic animal, which gene expression analysis suggests most closely resembles human luminal breast cancer [17] which form ER+ tumors after orthotopic implantation [18].