THE INTERACTION OF EPIDERMAL GROWTH-FACTOR AND RADIATION IN HUMAN HEAD AND NECK SQUAMOUS-CELL CARCINOMA CELL-LINES WITH VASTLY DIFFERENT RADIOSENSITIVITIES

Purpose: This study was performed to characterize the interaction of e pidermal growth factor and radiation in two human head and neck squamo us cell cancer cell lines of vastly different radiosensitivities (UM-S CC-6 Radiosensitive; UM-SCC-1 radioresistant). Methods and Materials: 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, cel l survival was assessed by a standard colony formation assay. Growth i nhibition was assessed by monitoring cell counts following treatment a nd flow cytometry was used to assess cell cycle distributions. Results and Conclusion: It was determined that exposure to epidermal growth f actor (10 ng/ml) for 24 h prior to radiation resulted in radiosensitiz ation in both cell lines, however, the magnitude of radiosensitization was greater in the radiosensitive UM-SCC-B cells compared to the radi oresistant UM-SCC-1 cells. Treatment of the UM-SCC-6 cells with epider mal 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 n o growth inhibition. The 24 h preradiation 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 w ill be necessary to determine whether events associated with the EGF-i nduced growth delay in the UM-SCC-6 cells are associated with the enha nced EGF-induced radiosensitization in these cells compared to UM-SCC- 1 cells.