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  • Title: 0.3 keV carbon K ultrasoft X-rays are four times more effective than gamma-rays when inducing oncogenic cell transformation at low doses.
    Author: Frankenberg D, Kühn H, Frankenberg-Schwager M, Lenhard W, Beckonert S.
    Journal: Int J Radiat Biol; 1995 Dec; 68(6):593-601. PubMed ID: 8551101.
    Abstract:
    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.
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