Radiation response of primary human skin fibroblasts and their bystander cells after exposure to counted particles at low and high LET.
OBJECTIVE
To investigate the dependence of bystander effects on linear energy transfer (LET) in the low dose region.


METHODS
The single-ion microbeam of the Physikalisch-Technische Bundesanstalt (PTB) was used to irradiate confluent primary human skin fibroblasts. Cells plated on a special irradiation dish were targeted with 10 MeV protons (LET 4.7 keV/microm) and 4.5 MeV a-particles (LET 100 keV/microm). During exposure, the cells were confluent allowing signal transfers through both gap junctions and diffusion.


RESULTS
For 10 MeV protons the clonogenic capability was significantly higher after exposure to 70 protons (0.31 Gy) compared with unirradiated cells. For higher doses the survival curve was exponential. Exposure of only 10% of all nuclei resulted in a similar radiation response in the low dose region. For higher doses up to 2.2 Gy no cell killing was observed. For 4.5 MeV alpha-particles an exponential survival curve was obtained. Irradiation of only 10% of all cell nuclei resulted in an survival curve as had been expected in the absence of any bystander effect.


CONCLUSIONS
The type and extent of bystander effects turned out to be dependent on the particles' LET and are likely to depend also on the cell line used and the techniques applied.
Physikalisch-Technische Bundesanstalt, Braunschweig, Germany. Dieter.Frankenberg@ptb.de
Dieter
D
Frankenberg
Klaus-Dieter
KD
Greif
Ulrich
U
Giesen
D000512:Alpha Particles; D024201:Bystander Effect; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D004260:DNA Repair; D005347:Fibroblasts / Q000528:radiation effects*; D006801:Humans; D018499:Linear Energy Transfer; D011522:Protons
D011522:Protons