An Integrative Bioinformatics Framework Prioritises a Gingival Mesenchymal Stem Cell Paracrine Apoptosis-ROS Axis in HPV-Negative Oral Squamous Cell Carcinoma: Preliminary Experimental Support and Repurposable-Drug Hypotheses.

Oral squamous cell carcinoma (OSCC) accounts for most head-and-neck cancers, and effective biological adjuvants remain limited. Gingival mesenchymal stem cells (GMSCs) exhibit anti-tumour paracrine activity, but the underlying molecular mechanisms and their relevance in patient cohorts remain incompletely understood. Consensus apoptosis-reactive oxygen species (ROS) effectors were identified through integrated transcriptomic analyses of TCGA-HNSC and three GEO cohorts. Candidate genes were evaluated in primary OSCC cells exposed to GMSC-conditioned medium or indirect Transwell co-culture. Findings were further examined using patient-cohort validation, single-cell ligand-receptor analysis, pathway and transcription-factor activity inference, and drug-repurposing approaches. Computational analyses identified an apoptosis-ROS network centred on BAX, BCL2, CASP3, CASP9, NOX1, and GPX1. Indirect GMSC co-culture reduced intracellular ROS, increased early apoptosis, and induced G2/M accumulation, whereas conditioned medium produced inconsistent effects, suggesting a requirement for live bidirectional paracrine signalling. BAX was the only consistently up-regulated effector. The axis demonstrated concordant differential expression across independent HPV-negative OSCC cohorts but was not independently prognostic under leakage-free cross-validation or external validation. Pathway analyses supported ROS suppression, apoptosis activation, and altered stromal-tumour communication. Drug-repurposing analyses identified HSP90 inhibitors and the FDA-approved TOP2 inhibitor mitoxantrone as candidate therapeutic agents. GMSC paracrine activity targets a biologically interpretable apoptosis-ROS axis in OSCC that is reproducibly expressed across patient cohorts but does not constitute an independent prognostic biomarker. The identified therapeutic candidates warrant further experimental investigation.