The interaction of epidermal growth factor and radiation in human head and neck squamous cell carcinoma cell lines with vastly different radiosensitivities.

Abstract

This study was performed to characterize the interaction of epidermal growth factor and radiation in two human head and neck squamous cell cancer cell lines of vastly different radiosensitivities (UM-SCC-6 Radiosensitive; UM-SCC-1 radioresistant). The two human head and neck squamous cell cancers (UM-SCC-1 and UM-SCC-6) were grown in medium and following the appropriate treatments, cell survival was assessed by a standard colony formation assay. Growth inhibition was assessed by monitoring cell counts following treatment and flow cytometry was used to assess cell cycle distributions. It was determined that exposure to epidermal growth factor (10 ng/ml) for 24 h prior to radiation resulted in radiosensitization in both cell lines, however, the magnitude of radiosensitization was greater in the radiosensitive UM-SCC-6 cells compared to the radioresistant UM-SCC-1 cells. Treatment of the UM-SCC-6 cells with epidermal growth factor (EGF) (10 ng/ml) for 24 h resulted in a growth delay, however, cell growth returned to normal approximately 24 h following removal of EGF. Similar treatment of the UM-SCC-1 cells resulted in no growth inhibition. The 24 h pre-radiation exposures to EGF (10 ng/ml) did not affect the radiation-induced growth delay in either cell line. Additionally, the 24 h exposures to EGF (10 ng/ml) did not affect the radiation-induced growth delay in either cell line. Additionally, the 24 h exposures to EGF (10 ng/ml) did not cause the cells to enter a more radiosensitive cell cycle phase. Further work will be necessary to determine whether events associated with the EGF-induced growth delay in the UM-SCC-6 cells are associated with the enhanced EGF-induced radiosensitization in these cells compared to UM-SCC-1 cells.