Perineural invasion is a prominent clinical feature of various cancers, which causes difficulty in curative resection. Glial cell-derived neurotrophic factor (GDNF), a potent neurotrophic factor, plays an important role in the invasive and metastatic behavior of various cancers. The aim of this study was to examine the role of GDNF on oral squamous cell carcinoma.
Materials and Methods
GDNF expression in tissue samples was analyzed by immunohistochemistry. Transwell assay, zymography, Western blot, reverse transcription-PCR, and electrophoretic mobility shift assay (EMSA) were carried out to assess the effects of GDNF on oral cancer cells.
Human oral cancer tissues showed higher GDNF expression than that in normal tissues. We also found that application of human GDNF enhanced the cell migration ability of human oral cancers. Moreover, treatment with GDNF increased matrix metalloproteinase (MMP)-9 and MMP-13 expression in oral cancer. Inhibition of MMP-9 and MMP-13 in oral cancer cells by pharmacological inhibitors or neutralizing antibodies reduced GDNF-enhanced cell migration. Moreover, transfection with siRNA against MMP-13 inhibited GDNF-enhanced cell migration. Treatment with GDNF also increased ERK, p38 and JNK phosphorylation, and AP-1 DNA binding activity in human oral cancer cells. Inhibition of MAP kinase or AP-1 also reduced GDNF-induced oral cancer cell migration. In migration-prone sublines, oral cancer cells showed a higher migration ability than that of the original oral cancer cells. Surprisingly, the enhancement of cell migratory activity in migration-prone sublines was reduced by a GDNF-neutralizing antibody. Importantly, migration-prone sublines of oral cancer revealed higher GDNF expression.