KRT31 and familial pancreatic carcinoma: Here, we show that pancreatic cancer cells also express gastric H+,K+-ATPase subunits HKα1 and HKβ and non-gastric HKα2 coded by ATP4A, ATP4B and ATP12A. First, this indicates their ductal phenotype, and second, it indicates that they have transporters necessary for H+ extrusion, enabling them to survive in the acidic tumor microenvironment and most likely contribute significantly to this acidosis.