Western blot and RT-PCR analyses confirmed that arginase activity from mRCC cell lines was attributable solely to arginase II and not to arginase I. This is an important finding, since most studies have demonstrated that only arginase I produced by tumor cells, macrophages, smooth muscle and endothelial cells [26-29] is capable of depleting L-arginine which results in the induction of T-cell dysfunction [19,30]. Here, ARG2 is linked to neoplasm.