INDUCTION OF CISPLATINUM SENSITIVITY WITHOUT ALTERATION IN RADIATION SENSITIVITY BY FRACTIONATED RADIATION TREATMENT OF A HUMAN LARYNGEAL SQUAMOUS-CELL CARCINOMA CELL-LINE

Purpose: To determine if fractionated radiation treatment can alter ci splatinum sensitivity of a human laryngeal squamous carcinoma cell lin e. Methods and Materials: Human squamous carcinoma cells, both previou sly untreated, as well as survivors of fractionated radiation therapy, were tested in vitro for their sensitivity to gamma radiation and cis platinum. Fractionated gamma radiation was delivered in 14 or 10 daily fractions of 2 Gy. The cell line, cSCC-20, was derived from an untrea ted primary human laryngeal carcinoma. Results: The human laryngeal sq uamous cell carcinoma cell line, cSCC-20, was demonstrated to have het erogeneous subpopulations with respect to cisplatinum sensitivity. No variation in radiation sensitivity was seen among subpopulations of va rying cisplatinum sensitivity. The cells were relatively radioresistan t (Do = 2.5 Gy). Fractionated radiation treatments of the parent cell line (14 fractions, 14 days, 2 Gy/fraction) or a cisplatinum sensitive subline (10 fractions, 12 days, 2 Gy/fraction) induced cisplatinum se nsitivity (factor of 1.3 to 1.4) in the surviving cells. Conclusion: F ractionated radiation treatment of human squamous carcinoma cells in v itro induced sensitivity to cisplatinum without concomitant alteration in radiation sensitivity.