KRT19 and Patent ductus arteriosus: We demonstrated that the mouse PDA tumor was a suitable model for this analysis by showing that the KRT19+ cancer cells in subcutaneous (s/c) PDA tumors were coated with CXCL12, as assessed by imaging nonpermeabilized sections that had been stained with antibodies to KRT19 and CXCL12 (SI Appendix, Fig. S5 A and B).