SIRT1 and pachyonychia congenita: In this positive feedback loop, circZNF91 upregulated SIRT1 expression via competitively binding to miR-23b-3p and SIRT1 stabilizes HIF-1α protein via decreasing the acetylation of HIF-1α in pancreatic carcinoma (PC) cells,thus increasing the protein level of HIF-1α.