Objective To investigate the expression of Tropomyosin 4(TPM4)in thyroid cancer and its effects on the invasion and migration of thyroid cancer cells.Methods The expression level and prognostic value of TPM4 in thyroid cancer were analyzed based on bioinformatics,and its functional involvement was explored through Gene Set Enrichment Analysis(GSEA).In thyroid cancer K1 cells,lentiviral transfection was performed to establish the experimental group(TPM4 shRNA),the negative control group(empty lentiviral transfection),and the control group(untreated).Cell viability and proliferation were assessed using CCK-8 and BrdU assays.Transwell migration and invasion assays were performed to evaluate the effects of TPM4 on the migratory and invasive capacities of thyroid cancer cells.Results TPM4 expression was significantly upregulated in thyroid cancer(P<0.05)and correlated with TNM staging(P<0.05).Patients with higher TPM4 expression in advanced TNM stages exhibited poorer prognosis(P<0.05).GSEA results indicated that high TPM4 expression was enriched in gene sets associated with epithelial-mesenchymal transition,inflammatory response,P53 signaling pathway,and cell cycle.Following TPM4 knockdown in K1 cells,thyroid cancer cell growth was slowed(P<0.01),proliferative activity was decreased(P<0.001),and invasion and migration abilities were significantly impaired(P<0.001).Conclusion TPM4 is highly expressed in thyroid cancer and promotes the invasion and migration capabilities of thyroid cancer cells.