CTLA4 and colorectal carcinoma: Helios, associated with Treg cell thymic origin, is highly expressed in CRC Foxp3hi TI-Treg cells which also co-express activation markers such as ICOS and OX-40, and inhibitory molecules such as PD-1, CTLA-4, TIM-3 (Figure 1G), and CD39 that mediate their highly suppressive phenotype (Figure 1F) (148).