MiR-7-5p functions as a tumor suppressor by targeting SOX18 in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies. Recently, many kinds of microRNAs (miRNAs) have been found to play a significant role in development of PDAC. However, there is no investigation about expression and function of miR-7-5p in PDAC. In this study, we found that miR-7-5p was down-regulated in PDAC tissues and its low expression level indicated a poor survival rate for PDAC patients. By bioinformatic analysis, we found that miR-7-5p targeted SOX18, and there was a negative correlation between them in PDAC tissues. Then luciferase reporter and western blot assays were used to verify the binding of miR-7-5p on SOX18 3'UTR. Cell function assays demonstrated that miR-7-5p inhibited proliferation, migration and invasion of PANC-1 cells by targeting SOX18. The nude mouse tumorigenicity assay further proved that miR-7-5p targeted SOX18 to inhibit pancreatic cancer growth in vivo. In order to further understand the mechanism, we applied a transcription factor prediction tool to explore the underlying targets that transcripted by SOX18, and the result indicated that SOX18 was a transcription factor for gp130 (a subunit of IL-6 receptor), and ChIP assays was performed to prove this prediction. Furthermore, we detected the suppression of gp130/JAK2/STAT3 signaling pathway after silencing SOX18 in PANC-1 cells, which demonstrated the transcriptional activation role of SOX18 on gp130. Thus, our present study revealed that miR-7-5p targeted SOX18 to inhibit gp130/JAK2/STAT3 signaling pathway to exert its suppressing role in PDAC.