Growth differentiation factor 15 as a radiation-induced marker in oral carcinoma increasing radiation resistance

BACKGROUND: Growth differentiation factor 15 (GDF15) is involved in tumor pathogenesis of oral squamous cell carcinoma (OSCC). The aim of this study was an investigation of the potential influence of GDF15 on radioresistance of OSCC cells in vitro. METHODS: Oral squamous cell carcinoma cell lines were irradiated with 0, 2, or 6 Gy, and GDF15 expression in the supernatant per survived cell colony was examined with ELISA. Non-irradiated and OSCC cell lines irradiated with 6 Gy were evaluated for GDF15 expression using immunofluorescent staining. For further investigation of GDF15 effects on radioresistance, a GDF15 knockdown model in a human OSCC cell line was established, and apoptotic activity after radiation was measured using the Caspase-Glo 3/7 system. RESULTS: ELISA and immunofluorescent staining indicated an increased GDF15 expression in 5 OSCC cell lines compared with human gingival epithelial cells. Irradiation with two and six gray resulted in a significant elevation of GDF15 expression per survived cell colony in the irradiated OSCC cell lines (P < 0.001). Furthermore, a dose-dependent expression of GDF15 was seen. Immunofluorescent staining confirmed an elevated GDF15 expression in irradiated OSCC cell lines (n = 10; P <= 0.001). Apoptotic activity was significantly increased after irradiation in the GDF15 knockdown group compared with control cells (n = 24; P < 0.001). CONCLUSION: This study describes for the first time the vital role of GDF15 both in tumorigenesis and in radioresistance of OSCC cells. With its anti-apoptotic effects, GDF15 possibly promotes tumor progression and might protect carcinoma cells against irradiation effects. Consequently, GDF15 may be a promising therapeutic target in oral cancer.