Abstract 4777: Core tension and control: Fxr1 mediates mechanoregulation via ahnak in head and neck cancer

Abstract Background: Head and neck squamous cell carcinoma (HNSCC) is the sixth most prevalent cancer globally and is marked by aggressive invasion, high metastatic potential, and a persistently low 5-year survival rate (∼50%). Emerging evidence highlights the roles of cytoskeletal remodeling and altered cellular biomechanics, including stiffness, viscoelasticity, and deformability, in promoting cancer cell migration and invasion. However, the molecular regulators of these biomechanical properties in HNSCC remain poorly defined. Methods: We investigated the role of Fragile X-Related Protein 1 (FXR1), an RNA-binding protein, in modulating tumor biomechanics and invasion in cancer cells. FXR1 knockdown (KD) was performed in HNSCC cell lines, followed by transcriptomic, cytoskeletal, and biomechanical analyses. Functional assays, including cell motility, stiffness, and tumor growth in vitro and in syngeneic mouse models, were performed to define the tumorigenic role of FXR1 in oral cancer. Results: FXR1 silencing significantly upregulated AHNAK, a large scaffolding protein implicated in cytoskeletal organization. This upregulation was associated with reduced F-actin polymerization, impaired lamellipodia formation, decreased cellular stiffness, and diminished invasive and migratory properties of oral cancer cells. Dual knockdown of FXR1 and AHNAK partially restored F-actin architecture, lamellipodia formation, and cell stiffness, suggesting a functional interplay between the FXR1-associated protein network. Mechanistically, further evidence demonstrated that FXR1 KD activated the Hippo signaling pathway via LATS2, leading to the cytosolic accumulation of phosphorylated YAP (P-YAP), implicating FXR1's role in mechanotransduction. In vivo, WT and FXR1 KD-derived xenografts exhibited significantly reduced tumor volume in syngeneic mouse models with immune cell activation. Conclusions: FXR1 promotes HNSCC progression by repressing AHNAK and enhancing F-actin dynamics, thereby increasing cellular stiffness, invasion, and migration. Our findings reveal a novel FXR1-AHNAK-F-actin axis that regulates tumor biomechanics and invasiveness of oral tumors, offering new mechanistic insights and identifying FXR1 as a promising therapeutic target in HNSCC. Citation Format: Anitha Vijayakumar, Samuel John, Tae-Hyung Kim, Breege V. Howley, Viswanathan Palanisamy. Core tension and control: Fxr1 mediates mechanoregulation via ahnak in head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4777.