Abstract
The relative biologic effectiveness of model 6711 125I seeds (Ningbo Junan Pharmaceutical Technology Company, Ningbo, China) and their effects on growth, cell cycle, and apoptosis in human pancreatic cancer cell line PANC-1 were examined in the present study. PANC-1 cells were exposed to the absorbed doses of 1, 2, 4, 6, 8, and 10 Gy either with 125I seeds (initial dose rate, 2.59 cGy/h) or with 60Co γ-ray irradiation (dose rate, 221 cGy/min), respectively. Significantly greater numbers of apoptotic PANC-1 cells were detected following the continuous low-dose-rate (CLDR) irradiation of 125I seeds, compared with cells irradiated with identical doses of 60Co γ-ray. The D0 for 60Co γ-ray and 125I seed irradiation were 2.30 and 1.66, respectively. The survival fraction after 125I seed irradiation was significantly lower than that of 60Co γ-ray, with a relative biologic effectiveness of 1.39. PANC-1 cells were dose dependently arrested in the S-phase by 60Co γ-rays and in the G2/M phase by 125I seeds, 24 hour after irradiation. CLDR irradiation by 125I seeds was more effective in inducing cell apoptosis in PANC-1 cells than acute high-dose-rate 60Co γ irradiation. Interestingly, CLDR irradiation by 125I seeds can cause PANC-1 cell-cycle arrest at the G2/M phase and induce apoptosis, which may be an important mechanism underlying 125I seed–induced PANC-1 cell inhibition.