The mechanism of fibronectin 1 promoting papillary thyroid cancer progression by regulating anoikis resistance

Background: Papillary thyroid cancer is a common head and neck malignancy with a globally rising incidence. While most patients attain favorable prognosis following standard treatment, a subset develops recurrence and metastasis—two key factors that compromise clinical outcomes. Anoikis resistance is a prerequisite for tumor metastasis; however, the role and mechanism of Fibronectin 1 (FN1)—a molecule overexpressed in multiple cancers and linked to tumor progression—in papillary thyroid cancer anoikis resistance remain undefined. Objective: This study therefore investigated the function and regulatory mechanism of FN1 in papillary thyroid cancer anoikis resistance using a combination of bioinformatics analyses and experimental validation. Methods: First, using The Cancer Genome Atlas (TCGA) dataset and anoikis-related genes from GeneCards, we identified FN1 as an anoikis-related hub gene in thyroid cancer through bioinformatics analyses, including consensus clustering, weighted gene co-expression network analysis (WGCNA), and protein-protein interaction (PPI) network analysis. Its clinical relevance was further analyzed from the perspectives of pathological typing, survival prognosis, immune cell infiltration (via xCell) and single-cell expression patterns. Next, we performed validation using papillary thyroid cancer tissues, adjacent normal tissues, and cell lines (8305c, BCPAP, Nthy-ori 3 − 1): FN1 expression and cancer cell anoikis were detected by immunohistochemistry (IHC) and TUNEL staining; FN1 mRNA and protein levels were quantified via qRT-PCR and Western blot. Finally, we modulated FN1 expression through RNA interference (for knockdown). Cell proliferation, migration, and invasion were assessed using CCK-8 and Transwell assays, while Western blot was applied to measure the expression of apoptosis-related proteins. Results: FN1 is highly expressed in papillary thyroid cancer tissues and cell lines and is associated with poor tumor prognosis. Silencing FN1 can inhibit the proliferation, migration and invasion of papillary thyroid cancer cells and increase the anoikis rate. Overexpression of FN1 showed the opposite effect. Mechanistically, FN1 can up-regulate anti-apoptotic proteins BCL2L1 and Caspase-3, and down-regulate pro-apoptotic protein BAD, thereby enhancing anoikis resistance. Conclusions: FN1 is highly expressed in papillary thyroid cancer and correlates with poor prognosis. Mechanistically, FN1 enhances papillary thyroid cancer cell tumorigenic potential by regulating proliferation, migration, invasion and apoptotic progression via the BCL2L1/BAD axis, thus driving tumor development. FN1 may act as a promising therapeutic target for advanced papillary thyroid cancer.