Intriguingly, in an earlier study, simvastatin, a lipophilic statin, was found to not only act as a cancer vaccine adjuvant but also synergize anti PD-1 therapy in multiple animal models through decreasing the geranylgeranylation of small GTPases and regulating endosomal trafficking in dendritic cells which led to better antigen presentations (41) (Table 2). This evidence concerns the gene PDCD1 and cancer.