In organotypic cultures of normal human pancreatic cells (HPDE), parenchymal cancer cells (CPCs) and cancer stem cells (CSCs) growing on matrices reproducing ECM changes during progression, we studied resting pHi, the pHi response to fluxes of NaHCO3 and acidosis and the role of NHE1 in pHi regulation. The gene discussed is SLC9A1; the disease is cancer.