Background
Antigen presentation may be an important factor contributing to immune evasion in cancer. This study investigated antigen-presenting prognostic related genes (APPGs) and their potential mechanisms in hepatocellular carcinoma (HCC).
Conclusion
The results of this study show that APP.Score could be an independent prognostic factor for patients with HCC, and that PLA2G7 silencing inhibits cancer cell development and PD-L1 expression. We provide a new perspective and potential target for immune research on antigen presentation in HCC.
Methods
We constructed a score built upon the core APPGs (APP.Score) through nonnegative matrix factorization (NMF) clustering, weighted gene co-expression network analysis (WGCNA), random forest (RF), and least absolute shrinkage and selection operator (LASSO) methods. We also compared the clinical and molecular characteristics of different APP.Score. Furthermore, in vitro experiments were conducted to validate the expression of core APPGs and investigate the effects of phospholipase A2, group 7 (PLA2G7) knockdown on HCC cell development and programmed death-ligand 1 (PD-L1) expression.
Results
APP.Score was positively correlated with immune cell infiltration and levels of immune checkpoint inhibitor-related genes, and negatively correlated with overall survival (OS). The area under the curve values were 0.734, 0.747, and 0.679 for survival periods of 1, 2, and 3 years, respectively, indicating that APP.Score could be an independent prognostic factor for patients with HCC. OS of the high expression group of these genes, including PLA2G7, musculin, heat shock protein family A, secreted phosphoprotein 1, and neutrophil cytosolic factor 2 (NCF2) was lower than that of their low expression group. Moreover, the upregulation of key components of APPGs, except NCF2, was observed in HCC. The inhibition of PLA2G7 suppressed HCC progression and reduced PD-L1 and phosphorylated signal transducer and activator of transcription 1 (p-STAT1)/STAT1 levels in HepG2 and Huh-7 cells. Remarkably, the decrease in PD-L1 expression caused by PLA2G7 silencing was reversed upon treatment with a STAT1 activator.