Effect of siRNA-mediated knockdown of the PD-L1 (CD274) gene on DUSP gene family expression and potential clinical implications in gastric cancer.

This study aimed to investigate the molecular interaction between PD-L1 (CD274) and members of the dual-specificity phosphatase (DUSP) gene family (DUSP1, DUSP2, DUSP4, DUSP6, and DUSP10) in gastric adenocarcinoma (GC) using integrated bioinformatic and experimental approaches. Bioinformatic analyses based on UALCAN, GEPIA, TIMER 2.0, and STRING databases revealed significant dysregulation of PD-L1 (CD274), DUSP2, DUSP4, DUSP6, and DUSP10 in tumor tissues, while DUSP1 was downregulated. Gene expression patterns were associated with tumor stage and patient prognosis. Promoter methylation analyses suggested epigenetic regulation of PD-L1 (CD274), DUSP1, and DUSP2, and copy number variation analysis indicated that gene amplifications were associated with altered immune cell infiltration, particularly dendritic cells and T lymphocytes. Gene expression was further evaluated in gastric tumor and adjacent non-tumor tissues using the GEO dataset GSE27342. Functional validation using siRNA-mediated PD-L1 (CD274) knockdown in AGS gastric cancer cells (GC) resulted in reduced cell viability, induction of apoptosis, upregulation of DUSP4, and downregulation of DUSP2. qPCR analysis of patient-derived tissue samples demonstrated significant alteration of DUSP6 expression, while peripheral blood analysis revealed significant suppression of DUSP2 in GC patients compared to controls. Logistic regression and ROC analyses identified DUSP6 (tissue level) and DUSP2 (blood level) as the most statistically relevant markers among the evaluated genes. Collectively, these findings suggest that PD-L1 (CD274) influences tumor cell survival not only through immune checkpoint signaling but also through modulation of MAPK-associated phosphatases. The coordinated dysregulation of PD-L1 (CD274), DUSP2, and DUSP6 supports the existence of a functional PD-L1/DUSP signaling axis in gastric cancer pathogenesis and highlights its potential relevance for future diagnostic and therapeutic investigations.