Flow cytometry analysis demonstrated the expression of inhibitory receptor PD-1 on CD4+ and CD8+ T cells and its ligand PD-L1 on tumor cells in CT-2A-dmEGFRvIII-Luc and SMA560-dmEGFRvIII-Luc tumors (Additional file 1: Figure S4). This evidence concerns the gene PDCD1 and neoplasm.