EIF4E overexpression may confer radioresistance in a head and neck cancer cell line

Abstract Problem: Preliminary analysis of data showing that overexpression of eIF4E in surgical margins is an independent prognostic marker determined that patients with advanced stage disease that overexpress eIF4E in the margins do not seem to respond to radiation therapy and recur at a higher rate compared to eIF4E-negative margin patients. Hence we hypothesize that increased expression of eIF4E in the margins of head and neck squamous cell carcinoma (HNSCC) patients causes these cells to become radioresistant. Methods: Radiation survival curves were performed at 0, 2, 4, 6, 8, and 10 Gy using clonogenic assays in 2 HNSCC cell lines FaDu and HEp3 with varying levels of eIF4E. As these cell lines have different genetic backgrounds we also determined if modulating the expression of eIF4E alone, in HNSCC cell lines changes their radiation sensitivity in vitro. PCI-15a with low expression of eIF4E was stably transfected with sense RNA constructs to eIF4E: PCI-15a-MSCV neo eIF4E wild-type and its radiation sensitivity compared to mock PCI-15a-MSCV new empty vector using the MTS-PMS assay to determine the number of viable cells at 0, 2, 4, 6, 8, and 10 days postradiation (as cells would not grow in colonies). We determined expression of eIF4E by western blots after radiation and apoptosis was evaluated after radiation via flow cytometry using the CaspACE FITC-VAD-FMK In Situ Marker kit (Promega). Results: HEp3 with a 2.5-fold higher expression of 4E compared to FaDu was significantly more radioresistant at iÝ6 Gy ( P = 0.02). There was a 20% to 25% (significant). Conclusion: Overexpression of eIF4E appears to be associated with radiation resistance. Significance: Overexpression of eIF4E appears to be associated with radiation resistance. Support: None reported.