Given the role of CCR9 in controlling inflammatory processes in the colon, we hypothesized that CCR9 could also participate in the recruitment of the Treg subpopulations that modulate the development of CRC, Our findings demonstrate that the absence of CCR9 promotes the accumulation of Helios- Tregs and a decreased proportion of highly suppressive Helios+ Tregs within the tumor microenvironment. This evidence concerns the gene CCR9 and neoplasm.