Immune landscape of gingivo-buccal oral cancer indicates high enrichment of immune-related gene sets in tumors of a large proportion of patients

Oral squamous cell carcinoma of the gingivo-buccal region (OSCC-GB) is the most common cancer among males in India and the second most prevalent cancer overall. Therefore, there is an urgent need to develop precision therapies based on an evaluation of molecular heterogeneity and molecular subtyping. We performed bulk RNA-Seq on tumor and adjacent normal tissue samples from 72 OSCC-GB patients, as well as leukoplakia (precancerous) tissue from 25 patients with concurrent leukoplakia. Analysis of our data revealed activation of epithelial-mesenchymal transition, angiogenesis, and cell-cycle pathways. Metabolic analysis revealed enhanced glycolysis and reduced oxidative phosphorylation, consistent with the Warburg effect. Gene set enrichment analysis identified two distinct molecular subtypes, one of which comprises 76.4% of the patients. This subtype is characterized by higher immune cell infiltration, suggesting potential responsiveness to immune checkpoint inhibitors. Additionally, CD226, CD38, and KBTBD8 were identified as potential biomarkers for patient classification (average classification accuracy of 86.1%) and were validated in an independent cohort. The smaller number of patients (23.6%) who comprised the second subtype showed lower enrichment in immune-related gene sets. Pre-malignant leukoplakia tissues showed significantly higher M1 macrophages and CD4 + T-cells compared to normal tissues, indicating an activated host defense mechanism and potential for early intervention. TCGA-HNSC tumors also exhibited molecular heterogeneity; some subtypes were similar to OSCC-GB tumors and revealed shared enrichment of glycolysis and immune-related pathways. Our findings provide critical insights into the molecular and immune landscape of OSCC-GB, paving the way for improved therapeutic strategies and immunotherapy approaches.