IDO1 and Patent ductus arteriosus: Some PDA cells, for example CFPAC and HPAF II, were found to be resistant to the therapy and several genes were overexpressed in them such as indoleamine 2, 3-dioxygenases-1 (IDO1), cyclooxygenase 1 and 2 (CO × 1/2), and galectin-9 (Gal-9) [82].