Overexpression of DAPK1-mediated inhibition of IKKβ/CSN5/PD-L1 axis enhances natural killer cell killing ability and inhibits tumor immune evasion in gastric cancer

Gastric cancer (GC) originates from the stomach and is a prevalent human malignancy. Dysfunction of death associated protein kinase 1 (DAPK1) has been identified as a major regulator involved in the development and progression of GC. However, there's limited data regarding the regulatory mechanism of GC. Herein, we investigated role of DAPK1 in natural killer (NK) cell killing ability and immune evasion of GC cells and mediated pathway. Samples from GC-related gene expression profile and clinical samples from 67 patients with GC were collected to determine the expression of DAPK1, IκB kinase β (IKKβ), programmed death receptor-ligand 1 (PD-L1), and photomorphogenesis 9 (COP9) signalosome 5 (CSN5). The binding affinity among DAPK1, IKKβ, CSN5, and PD-L1 was characterized to verify the underlying mechanism. GC lines were transfected with overexpressed plasmid or siRNA to determine the effect of DAPK1/IKKβ/CSN5/PD-L1 axis on NK cell killing ability and immune evasion of GC cells. GC cells and tissues presented low expression of DAPK1 and high expression of IKKβ, CSN5 and PD-L1. IKKβ, negatively regulated by DAPK1, was capable of activating CSN5 and upregulating PD-L1 expression. Overexpression of DAPK1 promoted NK cell killing ability and reduced immune evasion, coupled with reduction of NK cell apoptosis and increases in levels of TNF-α, IFN-γ, CD107a, and Granzyme B cytokines. The tumor-suppressing properties of DAPK1 through downregulation of IKKβ/CSN5/PD-L1 axis in GC were further confirmed in vivo. In summary, overexpression of DAPK1 promoted the NK cell killing ability and restrained immune evasion of GC cells, providing a potential therapeutic strategy for GC treatment by modulating immune evasion.