Arginase II can be regulated by histone deacetylases in nonmalignant cells, therefore we hypothesised that the AZA/VOR may also downregulate arginase activity in AML blasts.10 Culture of AML cell lines with azacitidine and vorinostat did not decrease arginase enzyme activity (Fig. 2f) or supernatant arginine concentrations (Fig. 2g). Here, ARG2 is linked to acute myeloid leukemia.