The combination therapy of IL-17A and PD-1 antibodies significantly increased the CD8 +T cell population.37 Low-dose decitabine also enhanced the effect of PD-1 blockade in MSS CRC by re-modulating the tumor microenvironment.38 The lack of recruitment of immune cells (mainly CD8 +T cells) to the tumor seems to be the fundamental obstacle to ICB efficacy. This evidence concerns the gene PDCD1 and neoplasm.