LAG3 and cancer: Importantly, LAG-3 and PD-1 co-expression in T cells is a biomarker of strong T-cell dysfunctionality in cancer and it is associated with resistance to anti-PD-1/anti-PD-L1 immunotherapies.24, 25, 26, 27, 28, 29, 30 PD-1 and LAG-3 co-blockade increases many T-cell antitumor activities.26