A ‘Spicy’ Mechanotransduction Switch: Capsaicin-Activated TRPV1 Receptor Modulates Osteosarcoma Cell Behavior and Drug Sensitivity

Osteosarcoma (OS), the most common primary malignant bone tumor arising in the highly mechanosensitive bone tissue, exhibits marked heterogeneity and resistance to conventional therapies. While molecular drivers have been extensively characterized, the role of mechanical stimuli in OS progression remains underexplored. In this study, we identify the transient receptor potential vanilloid 1 (TRPV1) channel as a key regulator of mechanotransduction and drug responsiveness in OS cells. Using uniaxial cyclic stretch, we show that the highly aggressive U-2 OS cell model undergoes TRPV1-dependent perpendicular reorientation, in contrast to the inert response observed in the less aggressive SAOS-2 cells. Through confocal microscopy, immunohistochemistry, and atomic force microscopy, we demonstrate that nanomolar concentrations of capsaicin—a well-characterized TRPV1 agonist—chemically replicate the mechanical phenotype, altering metastatic traits such as cell adhesion, edge architecture, migration rate, nuclear-to-cytoplasmic ratio, and chemotherapeutic sensitivity to doxorubicin and cisplatin. TRPV1 activation, whether mechanical or chemical, elicits subtype-specific effects absent in healthy hFOB osteoblasts. Notably, it differentially regulates nuclear localization of the pro-to-oncogene Src in U-2 OS versus SAOS-2 cells. Parallel changes in Src and acetylated histone H3 (acH3) levels support a role for TRPV1 as a molecular switch in the Src–acH3 mechanosignaling axis. These TRPV1-mediated effects were not observed in non-malignant cells, underscoring their tumor specificity. Our findings position TRPV1 as a mechanosensitive signaling hub that integrates mechanical and chemical cues to drive epigenetic remodeling and phenotypic plasticity in OS, offering a potential therapeutic target—particularly in aggressive, drug-resistant subtypes.