Treatment of adoptively transferred CLL tumor cells with either recombinant PD-1 or anti-CD274 resulted in a significant reduction of transferred tumor cells at both 2- and 24-h time points in peripheral blood (both time points), as well as in the spleen, lymph nodes, and lungs (24-h time point) (51). Here, CD274 is linked to B-cell chronic lymphocytic leukemia.