Compared with the PBS group and the VVΔTK-STCΔN1L group, the expression of PD-L1 in the tumor was significantly increased after VVΔTK-STCΔN1L-mIL21 and VVΔTK-STCΔN1L-mIL21 + α-PD1 treatment, which gradually decreased as the treatment time passed (Figure 6B). This evidence concerns the gene CD274 and neoplasm.