Identification of potential biomarkers in follicular thyroid carcinoma: bioinformatics and immunohistochemical analyses

Objectives: The prevalence of thyroid cancer has shown a progressive rise over time. This study aimed to explore the expression and underlying mechanisms of decorin (DCN) in follicular thyroid carcinoma (FTC), employing bioinformatics analysis and immunohistochemistry techniques. Methods: The GSE27155 dataset was obtained from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) and core DEGs were identified through data mining and analysis using the R language and online databases. The expression of core DEGs was validated using The Cancer Genome Atlas database. Additionally, the correlation between DCN and clinicopathological stage, tumor-infiltrating lymphocytes, and hotspot molecules in thyroid cancer was assessed using the Gene Expression Profiling Interactive Analysis and TIMER databases. Immunohistochemical (IHC) analysis was then conducted to verify the differential expression of core DCN in FTC and adjacent tissues. Results: We confirmed the downregulation of three DEGs (DCN, GPC3, and PDGFRA). Furthermore, the analysis revealed a significant association between DCN expression and the clinical stage of patients with thyroid cancer (p<0.0001). DCN expression and the infiltration of several immune cells were positively correlated (p<0.01). A significant positive correlation was also noted between DCN and the NRAS and KRAS genes (partial cor>0, p<0.05). Immunohistochemical analyses revealed a significantly lower staining score (3.071 +/- 2.493) for DCN protein in cancer tissues than that in adjacent tissues (8.643 +/- 2.094) (p<0.0001). Conclusions: DCN is underexpressed and contributes to tumor progression in FTC. Thus, DCN serves as a tumor suppressor gene in FTC and a promising therapeutic target.