Purpose: Radioresistance in response to radiotherapy leads to cancer recurrence and poor survival in hypopharyngeal carcinoma patients. Previous studies indicate that ionizing radiation (IR) can induce epithelial–mesenchymal transition (EMT) that promotes the radioresistance, migration and invasiveness of tumors. The aim of this study was to explore the role of Snail in EMT and acquired radioresistance in hypopharyngeal carcinoma.
Methods: Radioresistance human hypopharyngeal carcinoma cells (FaduRR) were previously established from the Fadu cell line. Radiosensitivity was measured by colony forming assay. Western blot and Quantitative real-time PCR were used to detect the expression of EMT phenotypes and AKT/GSK-3β/Snail signaling pathway related proteins in Fadu+4Gy and FaduRR cells. Transwell and wound-healing assays were used to measure cell migration and invasiveness. EMT-related proteins and Snail expression were assessed in 80 hypopharyngeal carcinoma patient samples from radiosensitive and radioresistance groups using immunohistochemistry. Snail was silenced to evaluate its effects on EMT, radioresistance, migration, and invasiveness of FaduRR cells.
Results: The molecular characteristics of EMT were observed following radiation treatment, with migration, invasiveness and radioresistance enhanced in Fadu+4Gy and FaduRR cells. Moreover, we demonstrated that IR-induced EMT by activating the AKT/GSK-3β/Snail signaling pathway and that Snail silencing reversed EMT and attenuated radioresistance in FaduRR cells. Significant differences in EMT-related proteins and Snail expression were observed between radiosensitive and resistant group.
Conclusion: We demonstrate that IR can trigger EMT and enhance the migration, invasiveness, and radioresistance of FaduRR cells through the AKT/GSK-3β/Snail axis. Snail silencing could attenuate these effects and represents a novel therapeutic target for EMT-induced radioresistance in hypopharyngeal carcinoma.
Keywords: hypopharyngeal carcinoma, epithelial-mesenchymal transition, AKT/GSK-3β/Snail, radioresistance, Snail