Interestingly, ARG1 activity evaluated at pH 7.1 positively correlated with tumor grade, increasing from a median activity of 29.6 mg/h of urea in HD to 85.4 mg/h in GII, 93.9 and 152.8 mg/h in GIII and GIV, arguing for ARG1 activity as a potential marker of glioma progression from grade III to GIV, although longitudinal studies are required to confirm and strengthen this conclusion. The gene discussed is ARG1; the disease is neoplasm.