In addition, recent evidence suggests that the early activation marker CD69 could play a role in Treg cell retention within tumours, as a large proportion of tumour‐infiltrating Treg cells express high levels of this protein.90 Indeed, CD69 has been shown to be crucial for T‐cell trafficking by interfering with the expression of S1P1, so preventing lymphocyte egress from peripheral tissues.91, 92 Interestingly, CD69 is also linked to Treg cell function as CD69‐deficient Treg cells display an altered suppressive function in vitro and in vivo. This evidence concerns the gene S1PR1 and neoplasm.