PDCD1 and neoplasm: siRNAs have been reported to target different molecules on the surface of immune cells and tumor cells, including programmed cell death ligand-1 (PD-1) and its ligand PD-L1, as well as STAT3, which participate in the process of immune activation, to lessen tumor immune evasion and improve anti-tumor immunity (Nduom et al., 2016).