Using qRT–PCR and immunostaining analysis, we observed that CD44 was significantly up-regulated in PanIN lesions and PDA arising in AKC mice compared with KC lesions, while CD44 was not significantly expressed in age-matched wild-type mice, ATDC mice, or KC and AKC littermates prior to PanIN formation (Fig. 4A; Supplemental Fig. 12A). The gene discussed is CD44; the disease is Patent ductus arteriosus.