ARG1 and neoplasm: The mean arginase activity in the small EV fraction obtained from the ascitic fluid collected from ID8-ARG1 tumor-bearing mice at weeks 3 (n = 3) and 7 (n = 4) was 2.08 mU/ml of ascites (Source Data File—Table 1), which is within the range of arginase activities observed in OvCa patients (Fig. 2f).