Furthermore, PD-1 expression on TILs, especially relative to tumor cell PD-L1 expression, is not a good predictive marker for PD-1/PD-L1 checkpoint blockade immunotherapy [40, 47, 52–55], and the function of these cells in many types of cancer, including TNBC, is not fully understood. The gene discussed is PDCD1; the disease is neoplasm.