PAK4 and Patent ductus arteriosus: PAK4-KO-induced changes in autophagy did not affect the apoptosis, death, and proliferation of PDA cells nor the expression of MHC I. Our finding that PAK4 KO increased the expression of MHC I by PDA cells warrants further study of whether the increased expression of MHC I translates into more efficient cancer cell killing by CD8+ T cells.