Analysis of (MC38) tumor infiltrating T regulatory cells From ERT2Cre control and ERT2CreTIM-3(FLEX4) KO mouse.

Increased activity or number of regulatory T cells (Treg) serves as a barrier to effective anti-tumor immunity. Although manipulation of Treg cells is a promising anticancer strategy, doing so while sparing general immune tolerance has been a challenge. Thus, identifying factors specifically expressed in tumor-infiltrating Treg is important for better understanding cancer pathogenesis and identifying novel therapeutic targets that enhance anti-tumor immunity. We show that Tim-3 expression on tumor Treg is required for the function and survival of these cells, in part through Akt activation and FOXO1 inactivation. Knocking out Tim-3 in Treg also leads to delayed CD8 T cell exhaustion and lower tumor burden, without altering peripheral homeostasis. Thus, Tim3-expressing Treg are a promising target to modulate tumor-specific immune responses.