重粒子線治療の最適化のための生物学研究-II.損傷修復と分割照射

We have studied repair or recover from cell damages produced heavy-ion irradiation using animals and cultured mammalian cells. Relationship between the acquisition of radioresistance and fractionated irradiation was studied in vivo mice crypt cell survival. The acquisition of radioresistance was suppressed by injection of bFGF antibody before irradiation, and induction of bFGF-R was increased after the 3rd or 11th irradiation in the fractionated irradiation. Kinetics of SLDR and LET dependency of PLDR were studied with in vitro culture cell survival. The SLDR kinetics was observed with split irradiation at the middle position of carbon 6-cm SOBP beam. Cell survival increased with increasing repair time between the split dose quickly up to 60 min and saturate, as well as another cases of carbon plus x-ray or x-ray plus x-ray irradiation. We also could found the PLDR for all LET beams tested, but any LET dependency on both tumor (HSG) and normal (GM5389) cells. OER of DNA damage in CHO cells was high before repair treatment, and quickly decreased to be around 3 for x-rays. However, the repair treatment did not show any change of OER for carbon beam (80 keV/um) and the values were around 2