In contrast, the enterotoxins BFT (Bacteroides fragilis enterotoxin) and IL-17 produced by Bacteroides fragilis induce the differentiation of monocytic myeloid-derived suppressor cells into intestinal epithelial cells, which can selectively upregulate arginase 1 (Arg1) and type 2 NO synthase (NOS2) to produce NO, inhibit T cell proliferation, and promote CRC generation (67). Here, ARG1 is linked to colorectal carcinoma.