Melatonin Suppresses Oral Squamous Cell Carcinomas Migration and Invasion through Blocking FGF19/FGFR 4 Signaling Pathway

Oral squamous cell carcinomas (OSCCs) are one of the most prevalent malignancies, with a low five-year survival rate, thus warranting more effective drugs or therapy to improve treatment outcomes. Melatonin has been demonstrated to exhibit oncostatic effects. In this study, we explored the anti-cancer effects of melatonin on OSCCs and the underlying mechanisms. A human tongue squamous cell carcinoma cell line (SCC-15) was treated with 2 mM melatonin, followed by transwell migration and invasion assays. Relative expression levels of Fibroblast Growth Factor 19 (FGF19) was identified by Cytokine Array and further verified by qPCR and Western blot. Overexpression and downregulation of FGF19 were obtained by adding exogenous hFGF19 and FGF19 shRNA lentivirus, respectively. Invasion and migration abilities of SCC-15 cells were suppressed by melatonin, in parallel with the decreased FGF19/FGFR4 expression level. Exogenous hFGF19 eliminated the inhibitory effects of melatonin on SCC-15 cells invasion and migration, while FGF19 knocking-down showed similar inhibitory activities with melatonin. This study proves that melatonin suppresses SCC-15 cells invasion and migration through blocking the FGF19/FGFR4 pathway, which enriches our knowledge on the anticancer effects of melatonin. Blocking the FGF19/FGFR4 pathway by melatonin could be a promising alternative for OSCCs prevention and management, which would facilitate further development of novel strategies to combat OSCCs.