PDCD1 and cancer: The expression level of PD-L1 in cancer cells in the oeDT plus pembrolizumab group was significantly higher than that in the oeDT group, but significantly lower than that in the shDT plus pembrolizumab group (p < 0.05); this finding indicated that oeDT combined with PD-1 mAbs can increase the expression of PD-L1 on the surface of cancer cells, promote T cell recognition of cancer cells, and enhance T cell antitumor immune response (Fig. 4).