PDGFRα ⁺ /Integrin α2 ⁺ Fibroblasts Orchestrate Tumor Budding in Oral Squamous Cell Carcinoma via Mechano‐Metabolic Symbiosis: E‐Cadherin/Integrin α2β1 Adhesion and Mitochondrial Transfer

ABSTRACT Tumor budding (TB), defined as single tumor cells or small clusters (≤4 cells) at the invasive front, is a strong adverse prognostic feature in oral squamous cell carcinoma (OSCC). However, the stromal regulators and molecular mechanisms that drive TB remain unclear. Here, we developed a tumor‐budding organoid (TBO) model that faithfully recapitulates the OSCC tumor‐stroma interface and budding dynamics. By integrating this model with single‐cell RNA sequencing (scRNA‐seq), in situ RNA sequencing (isRNA‐seq), and functional perturbations, we identify platelet‐derived growth factor receptor alpha ⁺ /integrin α2 ⁺ (PDGFRα ⁺ /integrin α2 ⁺ ) cancer‐associated fibroblasts (CAFs) as the key stromal subset promoting OSCC budding. OSCC cells recruit PDGFRα ⁺ CAFs through PDGFA/PDGFRα signaling. These CAFs engage OSCC cells through two complementary crosstalk pathways: (1) heterotypic E‐cadherin/integrin α2β1 adhesion that transmits biomechanical cues to activate YAP signaling and induce epithelial‐mesenchymal transition (EMT)‐like programs; and (2) tunneling nanotube (TNT)‐mediated mitochondrial transfer that enhances oxidative phosphorylation (OXPHOS) and bioenergetic supply in budding cells. Targeted inhibition of TNT‐mediated mitochondrial transfer markedly suppresses TB in TBO and xenograft models. Together, our results reveal a mechano‐metabolic symbiosis between PDGFRα ⁺ /integrin α2 ⁺ CAFs and OSCC cells that drives TB and provides actionable targets to block this aggressive metastatic precursor.