To the best of our knowledge, this is the first study to investigate in great detail the expression of FoxO1 and p27kip1 in human liver tissue of patients with non-cirrhotic and cirrhotic PBC. Finally, the interrelationship between FoxO1 and its possible downstream target p27kip1 was investigated in the livers of mice harboring a conditional deletion of FoxO1/3a/4. Here, FOXO1 is linked to primary biliary cholangitis.