After the co-culturing of CD4+ T cells with NC-OE and FSTL3-OE CRC cells, the proportion of Tregs (CD25+ Foxp3+ T cells) among CD4+ T cells increased in the FSTL3-OE group, while IDO1 inhibitor (1-MT) could weaken this change (Fig. 5E). Here, FSTL3 is linked to colorectal carcinoma.