Using cell-derived and patient-derived xenograft models of HER2+/ER- breast tumors, our previous pre-clinical work provides evidence that dual targeting of BCL-2 and BCL-XL, via ABT-737 [37] or ABT-263/navitoclax [38], enhanced the in vivo effectiveness of lapatinib [9] or T-DM1 [39]. This evidence concerns the gene ERBB2 and breast neoplasm.