This latter by itself did not promote apoptosis in any cell line tested (˂ 4% in all cases), but blocked arginine depletion9, markedly prevented the apoptotic cell death of tumor cells (over 88% inhibition) induced by recombinant human neutrophil arginase-1 (Fig. 1f), and inhibited significantly and to a great extent the apoptosis response induced by PMN-S in a number of human cancer cell lines derived from different tissues. This evidence concerns the gene ARG1 and cancer.