To study mechanisms of PARPi resistance in-vivo, we isolated Brca1- or Bard1-deficient breast tumor cells (hereafter referred to as “Brca1-def” and “Bard1-def”) derived from Brca1- or Bard1-conditionally deleted mice (Shakya et al, 2008) and injected these cells in the mammary glands of syngeneic B6/129F1 mice (Fig. 1). Here, BRCA1 is linked to breast neoplasm.