CPE/HYOU1 axis-activated Hippo-YAP signaling pathway suppresses PANoptosis to facilitate osteosarcoma progression.

PANoptotisis associates with antitumor immunity in osteosarcoma (OS). This study aims to identify PANoptosis-related prognostic biomarkers for OS and elucidate their downstream regulatory mechanisms. Therefore, open data of single-cell transcriptomics were comprehensively analyzed to identify PANoptosis-related key cells. Publicly available bulk transcriptomic data were integrated to establish prognostic signatures for OS. They were evaluated for their immune characteristics, expression specificity, downstream targets, and pathway activation patterns. Functional assays (immunofluorescence/flow cytometry/western blot/xenograft tumors) were conducted to examine effects of CPE knockdown on OS progression, PANoptosome assembly, and PANoptosis levels. Rescue experiments involving HYOU1 overexpression or Hippo-YAP activation were performed to elucidate the PANoptotic regulatory mechanisms in OS. Results of single-cell analysis revealed significant enrichment of both macrophages and osteoblasts in OS samples and particularly in the low PANoptotic score subgroup. Further integration with bulk RNA-sequencing data revealed four biomarkers (CPE, MDK, SERPINH1, and NPW) for OS prognosis. They exhibited predominant expression in osteoblasts and demonstrated potentials in predicting OS outcomes. Of which, CPE deficiency markedly suppressed OS progression while upregulating PANoptosis in vitro and in vivo. Mechanistically, CPE specifically enhanced HYOU1 protein stability by inhibiting the ubiquitin-proteasome degradation. Additionally, CPE activated the Hippo-YAP signaling pathway, promoting nuclear translocation and transcriptional activity of YAP. Overexpression of HYOU1 or addition of YAP agonist reversed the anti-tumor effects and promotion of PANoptosis mediated by CPE deficiency. To conclude, the four-gene signature demonstrated potentials to predict OS prognostic risk. Among them, CPE targets HYOU1 and activates Hippo-YAP signal to promote OS progression by blocking PANoptosis.