Objective:To explore the role of transgelin(TAGLN) in the occurrence and development of papillary thyroid carcinoma (PTC) and its possible signal pathway.Methods:One hundred cases of PTC tissues and corresponding paracancerous normal thyroid tissues were collected. Realtime quantitative PCR (RT-qPCR), Western blotting, and immunohistochemistry were used to analyze the expression of TAGLN in PTC tissues and corresponding paracancerous normal thyroid tissues. PTC cells were transfected with plasmid and shRNA lentivirus vector respectively to up-regulate or down-regulate the expression of TAGLN in order to detect the effects of them on the proliferation, invasion, and migration by cell proliferation assay(cell counting kit-8, CCK-8)and cell invasion and migration assays (Transwell). The effects of TAGLN on mitogen-activated protein kinase (MAPK)/extracellular-signal regulating kinase (ERK) signal pathway was detected with Western blotting.Results:RT-qPCR showed that there was no difference in the expression of TAGLN mRNA between PTC and corresponding paracancerous normal thyroid tissues ( P>0.05); Western blotting demonstrated that the expression of TAGLN protein in PTC tissues was significantly lower than that in corresponding paracancerous normal thyroid tissues ( P<0.01). Immunohistochemical results revealed that the expression of TAGLN in PTC tissues was significantly lower than that in corresponding paracancerous normal thyroid tissues. Overexpression of TAGLN inhibited the proliferation, invasion, and migration of PTC cells ( P<0.01), but knockdown of TAGLN promoted the proliferation, invasion, and migration of PTC cells ( P<0.01). Overexpression of TAGLN decreased the expression of phosphorylated ERK ( P<0.05), whereas silencing TAGLN increased phosphorylated ERK level in PTC cells( P<0.01). Conclusion:The expression of TAGLN in PTC is significantly decreased. It is related to the occurrence and development of PTC, and its mechanism may be related to MAPK/ERK signal pathway.