ATP6V1A and cancer: In addition to targeting the gastric acid pump, PPIs may inhibit vacuolar-type H+ ATPase (V-ATPase) activity to affect cancer cells homeostasis and counter the malignant behavior of cancer cells, including proliferation, migration, invasiveness and drug resistance (Martinez-Zaguilan et al., 1993; Luciani et al., 2004; Sennoune et al., 2004; Huang et al., 2012).