SIRT1 and pancreatic neoplasm: The mechanism is that the hypoxia‐induced exosome circZNF91 can be transfected into normoxic pancreatic cancer cells and competitively binds to miR‐23b‐3p, which leads to the upregulation of sirtuin 1 (SIRT1) and thereby enhances the deacetylation‐dependent stability of the HIF‐1α protein, resulting in the resistance of pancreatic cancer cells to GEM.