0.3 keV carbon K ultrasoft X-rays are four times more effective than gamma-rays when inducing oncogenic cell transformation at low doses.
Oncogenic transformation and inactivation were investigated in C3H10T1/2 mouse embryo fibroblasts exposed to proton-induced 0.28 keV carbon K (CK)-characteristic X-rays and 60Co gamma-rays as reference radiation at high dose-rate (2-3 and 0.7 Gy/min respectively). Both oncogenic cell transformation and cell inactivation followed a linear-quadratic relationship with dose. At low doses where the linear component dominates CK ultrasoft X-rays were more effective, by a factor of 4, at inducing oncogenic cell transformation and cell inactivation compared with 60Co gamma-rays. For both endpoints the RBE of CK ultrasoft X-rays gradually decreased with increasing dose mainly due to the greater quadratic component for 60Co gamma-rays compared with CK ultrasoft X-rays. Our experimental data are in agreement with the hypothesis that single DNA double-strand breaks (dsbs), which are induced by 0.28-keV ultrasoft CK X-rays, may lead to oncogenic cell transformation. With increasing absorbed dose, i.e. with decreasing mean distance between dsbs induced by 0.28-keV ultrasoft X-rays, oncogenic cell transformation and cell inactivation may also be induced by interaction between those dsbs.
Frankenberg
D
D
Klinische Strahlenbiologie und Strahlenphysik, University of Göttingen, Germany.
Kühn
H
H
Frankenberg-Schwager
M
M
Lenhard
W
W
Beckonert
S
S
D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D002471:Cell Transformation, Neoplastic / Q000528:radiation effects*; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D051379:Mice; D008809:Mice, Inbred C3H; D014965:X-Rays