Radiosensitivity of human biliary tract cancer cell lines in vitro

The prognosis of biliary tract cancer is still poor. Although a number of clinical studies have suggested a role for radiation therapy in advanced biliary tract cancer, its value remains controversial. Moreover, the intrinsic radiosensitivity of bile duct cancer cell lines has not been described, and the molecular basis for the response of these tumors to ionizing radiation is poorly understood. The present study was designed to examine the intrinsic radiation sensitivity of human biliary tract cancer cells and its relationship to p53 status. Radiation response expressed by the parameters n, D₀, D₁₀, α, b, D̄ (mean inactivation dose), and SF₂ of seven cell lines derived from gallbladder and bile duct cancers was determined. The results suggest that biliary tract cancer cell lines as a group are relatively radioresistant. The mean X-ray survival parameters for these seven cancer cell lines were D₀ = 2.13 ± 0.29 Gy, D₁₀ = 5.73 ± 0.59 Gy, D̄ = 2.76 ± 0.25 Gy, α = 0.25 ± 0.03, and SF₂ = 0.54 ± 0.05. One of the seven lines was more radiosensitive than the others (D₀ = 0.77 ± 0.02 Gy, D₁₀ = 2.95 ± 0.06 Gy, D̄ = 1.57 Gy, α = 0.35, SF₂ = 0.35 ± 0.03). Five of six lines examined expressed mutant p53 including the radiosensitive line; one radioresistant line expressed wild-type p53. Thus, although loss of wild-type p53 expression occurred frequently in these biliary cancer cell lines, radiosensitivity did not correlate with p53 status. In view of the intrinsic radioresistance of this type of tumor cell coupled with the poor tolerance of surrounding normal tissues, maximal surgical debulking and intraoperative radiation therapy may contribute to increased local control over resection and/or conventional fractionated radiotherapy.