CALCA and neoplasm: To validate our findings in vivo and dissect tumor–stroma crosstalk by DKK3 status, we used an orthotopic 2 × 2 factorial cross‐transplant design: malignant cells from endpoint KC or DDKC tumors were orthotopically implanted into the pancreata of wild‐type or Dkk3‐null hosts, generating four groups (KC→WT, KC→DD, DDKC→WT, DDKC→DD) and isolating DKK3 contributions from tumor versus stroma (Figure6A; Figure S6A, Supporting Information).