Low doses of diagnostic energy X-rays protect against neoplastic transformation in vitro

Abstract

Low doses (< 1 cGy) of 60 kVp X-rays protect HeLa x skin fibroblast human hybrid cells against neoplastic transformation in vitro.

Linear No-Threshold Model vs. Radiation Hormesis

“…Controlled in-vitro and animal studies have contradicted the LNT model as many of these have shown adaptive response to low dose radiation resulting in reduced mutations and cancers (Hosoi and Sakamoto, 1993;Ishii et al, 1996;Mitchel et al, 1999;Redpath et al, 2003;Elmore et al, 2005;Day et al, 2007;Moskalev et al, 2011;Phan, 2011;Phan et al, 2012), demonstrating a phenomenon known as radiation hormesis (Luckey, 1980;Luckey, 1991;Calabrese and Baldwin, 2003;Feinendegen, 2005;Jolly and Meyer, 2009;Sanders, 2010). For humans, the effect of radiation on cancer has been inferred by determining the cancer rates of population groups that were exposed to radi-ation, and comparing these to equivalent population groups not exposed to the radiation.…”

Low dose gamma irradiation enhances defined signaling components of intercellular reactive oxygen-mediated apoptosis induction

“…They thus might represent the basis for the protective low dose radiation effects observed in vitro and in vivo [32][33][34][35][36][37][38][39][40][41][42][43][44]. However, it is also shown in this paper that cells with certain specific signaling features, ratios between specific signaling components as well as certain situations with respect to the density of cells may lead to protection of malignant cells rather than to their destruction.…”

“…There is an ongoing discussion on the effects of low dose radiation during carcinogenesis [31,32]. Potential controlling effects of low dose radiation on transformation and tumorigenesis have been well established in the literature [33][34][35][36][37][38][39][40][41][42][43][44]. Low dose radiation has been shown to induce a decrease in observable transformation frequency [33-36.41-43].…”

An Examination of Radiation Hormesis Mechanisms Using a Multistage Carcinogenesis Model

“…These in vitro experiments show a reduction of induced transformation frequencies at low doses to values below that observed spontaneously (Azzam et al, 1996;Redpath and Antoniono, 1998;Redpath et al, 2001Redpath et al, , 2003aRedpath et al, , 2003b. DNA repair mechanisms are highly conserved among all eukaryotes (Mitchel, 1995;Mitchel et al, 1997), and if these phenomena arise as the result of adaptations in DNA repair, it is not unreasonable to expect that some or all of these phenomena will also occur in humans.…”

“…In this section, the genomic instability model is extended to account for putative toxicant-induced adaptations in cellular repair systems as well as for toxicant-induced adaptations in the radical scavenging capacity of a cell. The experimental evidence suggesting the existence of radioprotective effects mainly comes from experiments performed with low doses of low-linear-energy-transfer (LET) radiation (e.g., Azzam et al, 1994aAzzam et al, , 1996Redpath and Antoniono, 1998;Redpath et al, 2001Redpath et al, , 2003aRedpath et al, , 2003bMitchel et al, 2003;Pant et al, 2003), and the proposed model may be more appropriate for-and X-rays than for high-LET radiations, such as α-particles from randon progeny.…”