PDCD1 and neoplasm: As immunotherapy-induced anti-tumor immune responses depend on the expression of PD-1 and its ligands (i.e., PD-L1/2) [27], we first analyzed the expression of the PDCD1 (encoding PD-1), PDCD1LG1 (encoding PD-L1) and PDCD1LG2 (encoding PD-L2) genes in TNBC tumor samples expressing TSP1 at low or high levels from the TCGA database.