ARG1 and cancer: Based on the observations that arginase inhibits T cell in the tumor microenvironment and thus promot cancer growth, novel immunotherapy vaccines targeting Arg1 or Arg2 have been developed and are now undergoing clinical trials (Martinenaite et al, 2019; Weis-Banke et al, 2020; Lorentzen et al, 2022; Niu et al, 2022).