AE2 might extrude HCO3− in exchange to osmotically active Cl– to support cell swelling.11,72 CAIX, which directly interacts with NBCe1 and AE2 at the leading edge of migrating cancer cells, could provide (or remove) HCO3− to (from) the transporters to support their transport activity. This evidence concerns the gene SLC4A4 and cancer.