The comparison between Id1-/- and Id1+/+ LLC Id1sh tumor-bearing mice (n per group = 8) showed that the lack of Id1 in both tumor cells and tumor microenvironment significantly potentiated the antitumor activity of anti-PD-1 therapy (Id1-/-/DPBS p = 0.0207; Id1+/+/anti-PD-1 p = 0.0269; Id1+/+/DPBS p = 0.0017) (Figure 3D,E). This evidence concerns the gene ID1 and neoplasm.