Using the Cellranger toolkit (10× Genomics), followed by marker gene annotation, we identified six distinct BC subpopulations, which were confirmed to originate from the respiratory lineage (Epcam +Nkx2-1+) and to express established adult BC markers (Trp63, Krt5, Aqp5, Aqp3, and Pdpn) (Figure 1—figure supplement 1C). Here, PDPN is linked to breast cancer.