Table 1 Efflux pumps described as hyperexpressed and/or hyperfunctional in malignant tumor cells or tumors

H+ATPase

Cytoplasm plasmamembrane and acidic organelles

Acidification of extracellular microenvironment and endo-lysosomal compartment

[21, 35]

Na+/H+ ATPase

Cytoplasm plasmamembrane

Alcalinization of cytosol and acidification of extracellular microenvironment

[51]

MCT1 (H+/Lactate symporters)

Cytoplasm plasmamembrane

Elimination of lactate as glucose catabolism product and acidification of extracellular milieu

[52]

Carbonic anhydrase

Cytoplasm plasmamembrane

Regulation of intracellular pH and pH gradients

[53]

H+/K+ ATPase

Gastric parietal cells

Regulation of extratracellular pH

[54, 59]

ATP- binding cassette

Cytoplasm and intracellular membranes

Transport and extrusion of chemotherapeutic drugs

[55–58]