PCNA and lung adenocarcinoma: Transfected cells A549 overexpressing IL-37 cause low gene expression of MMT-9, PCNA, Ki-67, Cyclin D1 and CDK4, but elevated expression of caspace-3 and caspace-9. IL-37 inhibits the proliferation, migration and invasion of human lung adenocarcinoma A549 cells as well as the chemotaxis of Treg cells and promotes apoptosis of A549 cells