TAC1 and cancer: Of these, H<sup>+</sup>-ATPases, especially vacuolar H<sup>+</sup>-ATPase (V-ATPase), play critical roles in cancer progression, metastasis, and immune evasion, while Na<sup>+</sup>/K<sup>+</sup>-ATPase (NKA) interacts with ion channels and H<sup>+</sup>-ATPase and hence contributes to antitumor immune responses.