BRCA1 mutation-carriers are predisposed to develop Basal-like breast cancer (BLBC), and p53 mutations are present in the majority of human BLBC cases, suggesting loss of these two tumor suppressors play key roles in development of BLBC. Recent studies suggest that the majority of human breast cancers, including BLBC, may originate from mammary epithelial cells (MECs) in the luminal lineage. However, how loss of p53 and BRCA1 contributes to development of BLBC from luminal MECs remains largely elusive. We developed a novel genetic targeting and lineage tracing approach based on intraductal injection of Cre-expressing adenovirus under the control of the pan-luminal Keratin 8 (K8) promoter (Ad-K8-Cre). We performed intraductal injection of Ad-K8-Cre to female mice carrying conditional knockout alleles of Brca1 (Brca1L) and Trp53 (Trp53L). The injected females developed mammary tumors similar to human BLBC within 12 months after injection. Here we characterized MECs targeted by Ad-K8-Cre one month after the intraductal injection. Overall design: YFP+ wild-type (WT), or p53-deficient, or p53/BRCA1-deficient mammary epithelial cells were sorted from Rosa26-Stop-YFP (R26Y), or Trp53L/L;R26Y, or Trp53L/L;Brca1L/L;R26Y female mice 1 month after intraductal induction of Ad-K8-Cre adenovirus, respectively; total RNAs were prepared from each sorted cell populations and subjected to RNAseq expression profiling.