While a small contribution of V-ATPase activity to pHi regulation has been reported in intact pancreatic ducts [53], our data are consistent with pHi recovery after an acid load being largely or fully accounted for by the activity of Na+/H+ exchangers and Na+-HCO3− cotransporters in most cancer cells [54,55] and with recent work showing that depletion of V-ATPases did not alter submembranous pH in Panc-1 cells [15]. This evidence concerns the gene SLC4A4 and cancer.