Fig. 1.

Schematic of a cancer cell, showing the major molecules involved in pH regulation. The complexity of the system is factually correct, but unpalatable for estimating the distribution of H⁺ ions fluxes through the various processes, deriving a value for the steady-state pH_i, or predicting how the system would respond to changes in one or more of these processes. MCT: H⁺-monocarboxylate transport; CA: carbonic anhydrase; CHE: Cl⁻/OH⁻ exchange; AE: anion exchange; NBCe: electrogenic Na⁺-HCO₃⁻ cotransport; NBCn: electroneutral Na⁺-HCO₃⁻ cotransport; NHE: Na⁺/H⁺ exchange; organelle: acidic lysosome/endosome with V-type ATPase