Development of TRAIL resistance by radiation-induced hypermethylation of DR4 CpG Island in recurrent laryngeal squamous cell carcinoma
International Journal of Radiation Oncology Biology Physics
Purpose There are limited therapeutic options for patients with recurrent head and neck cancer after radiation therapy failure. To assess the use of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) as a salvage chemotherapeutic agent for recurrent cancer after radiation failure, we investigated the effect of clinically relevant cumulative irradiation on TRAIL-induced apoptosis. Methods and Materials Using a previously established HN3 cell line from a laryngeal carcinoma patient, we generated a chronically irradiated HN3R isogenic cell line. Viability and apoptosis in HN3 and HN3R cells treated with TRAIL were analyzed with MTS and PI/annexin V-FITC assays. Western blotting and flow cytometry were used to determine the underlying mechanism of TRAIL resistance. DR4 expression was semiquantitatively scored in a tissue microarray with 107 laryngeal cancer specimens. Methylation-specific polymerase chain reaction and bisulfite sequencing for DR4 were performed for genomic DNA isolated from each cell line. Results HN3R cells were more resistant than HN3 cells to TRAIL-induced apoptosis because of significantly reduced levels of the DR4 receptor. The DR4 staining score in 37 salvage surgical specimens after radiation failure was lower in 70 surgical specimens without radiation treatment (3.03 ± 2.75 vs 5.46 ± 3.30, respectively; P<.001). HN3R cells had a methylated DR4 CpG island that was partially demethylated by the DNA demethylating agent 5-aza-2′-deoxycytidine. Conclusion Epigenetic silencing of the TRAIL receptor by hypermethylation of a DR4 CpG island might be an underlying mechanism for TRAIL resistance in recurrent laryngeal carcinoma treated with radiation. © 2014 Elsevier Inc. All rights reserved.
Lee, J., Lee, W., Min, Y., Cha, H., Han, M., Chang, H., Kim, S., Choi, S., Kim, S., & Kim, S. (2014). Development of TRAIL resistance by radiation-induced hypermethylation of DR4 CpG Island in recurrent laryngeal squamous cell carcinoma. International Journal of Radiation Oncology Biology Physics, 88 (5). http://dx.doi.org/10.1016/j.ijrobp.2013.12.016