Integrative Bulk and Single-Cell Transcriptomic Analysis Identifies a Hypoxia- and Lipid Metabolism-Related Prognostic Signature in Oral Squamous Cell Carcinoma: A Retrospective Study

Oral squamous cell carcinoma (OSCC) is a biologically heterogeneous malignancy with poor clinical outcomes. Hypoxia and lipid metabolic reprogramming are important drivers of OSCC progression and treatment adaptation, and these processes are biologically interconnected. However, prognostic studies integrating hypoxia- and lipid metabolism-related features in OSCC remain limited. Here, transcriptomic data from TCGA-HNSC-OSCC were integrated with curated hypoxia- and lipid metabolism-related genes to identify candidate genes, construct a prognostic signature, and characterize its biological relevance through enrichment analysis, immune profiling, single-cell RNA-sequencing analysis, and RT-qPCR validation. A four-gene signature consisting of STC2, CAV1, ACADL, and PLA2G2D showed stable prognostic performance in the TCGA-HNSC-OSCC cohort and the external validation cohort GSE41613. The risk signature remained significantly associated with overall survival after adjustment for clinicopathological factors and retained prognostic discrimination across stage- and nodal status-defined subgroups. The high- and low-risk groups displayed distinct pathway, immune, mutational, and predicted drug sensitivity features. Notably, PLA2G2D showed the strongest association with differential immune infiltration, whereas single-cell analysis identified endothelial cells as a major CAV1-enriched population with active intercellular communication and dynamic state transitions. These findings define a hypoxia- and lipid metabolism-related prognostic signature and support its relevance to immune remodeling and endothelial cell context in OSCC.