Pharmacological inhibition of the proton pump V-ATPase causes tumor necrosis in a Ewing’s sarcoma xenograft model. A. A673 cells were subcutaneously injected in NOD/SCID mice. Mice were then treated with different concentration of omeprazole, a V-ATPase inhibitor (0 mg/kg n = 14, 2.5 mg/kg n = 7, 10 mg/kg n = 14), to reduce intratumoral acidosis. H&E staining of tumor sections, representative images of the necrotic area, scale bar, 100 µm; B. Box plot of the tumor volume. Mean ± SE; C. Box plot of the tumor necrosis. Mean ± SE (*P < 0.05, **P < 0.01).