Using a novel mouse model of PDA combining low-level deregulated MYC expression with mutant KRAS (KMC), we find that deregulated MYC expression decreases survival and drives ductal-neuroendocrine lineage plasticity, while loss of one copy of Myc in the LSL-KrasG12D;P53R172H/+;Pdx1-Cre (KPC) mouse model suppresses ductal-neuroendocrine cells. The gene discussed is KRAS; the disease is Patent ductus arteriosus.