LAG3 and breast cancer: Recently, fibrinogen-like protein 1 (FGL1) has been identified as a high-affinity LAG3 ligand that can inhibit antigen-specific T cell responses and is upregulated in various cancers such as lung adenocarcinoma, prostate cancer, and breast cancer (172).Moreover, LAG3 has also been found on Treg cells, and blocking LAG3 diminishes suppressor function (173).