ARG1 and cancer: Nonetheless, increasing evidence shows that overexpression of ARG1/2 (with or without subsequent decline in serum L-arg concentrations) should be perceived as a poor prognostic factor in a wide variety of cancer types including head and neck cancer (62), neuroblastoma (46), acute myeloid leukemia (AML) (61), pancreatic ductal carcinoma (63), ovarian carcinoma (64), or colorectal cancer (65).