Sparsely Ionizing Diagnostic and Natural Background Radiations are Likely Preventing Cancer and other Genomic-Instability-Associated Diseases

Abstract

Routine diagnostic X-rays (e.g., chest X-rays, mammograms, computed tomography scans) and routine diagnostic nuclear medicine procedures using sparsely ionizing radiation forms (e.g., beta and gamma radiations) stimulate the removal of precancerous neo-plastically transformed and other genomically unstable cells from the body (medical radiation hormesis). The indicated radiation hormesis arises because radiation doses above an individual-specific stochastic threshold activate a system of cooperative protective processes that include high-fidelity DNA repair/apoptosis (presumed p53 related), an auxiliary apoptosis process (PAM process) that is presumed p53-independent, and stimulated immunity. These forms of induced protection are called adapted protection because they are associated with the radiation adaptive response. Diagnostic X-ray sources, other sources of sparsely ionizing radiation used in nuclear medicine diagnostic procedures, as well as radioisotope-labeled immunoglobulins could be used in conjunction with apoptosis-sensitizing agents (e.g., the natural phenolic compound resveratrol) in curing existing cancer via low-dose fractionated or low-dose, low-dose-rate therapy (therapeutic radiation hormesis). Evidence is provided to support the existence of both therapeutic (curing existing cancer) and medical (cancer prevention) radiation hormesis. Evidence is also provided demonstrating that exposure to environmental sparsely ionizing radiations, such as gamma rays, protect from cancer occurrence and the occurrence of other diseases via inducing adapted protection (environmental radiation hormesis).

Current Importance and Potential Use of Low Doses of Gamma Radiation in Forest Species

“…This radiation, above a stochastic threshold stimulate intracellular and intercellular signaling that leads to activated natural protection (ANP) against cancer and other genomic-instability-associated diseases (Scott, 2005;Scott & Di Palma, 2006).…”

Radiation-Stimulated Epigenetic Reprogramming of Adaptive-Response Genes in the Lung: An Evolutionary Gift for Mounting Adaptive Protection against Lung Cancer

“…Pathways that include induced p53-dependent high-fidelity DNA repair along with normal apoptosis (which eliminates seriously damaged cells), activation of an epigenetic protective apoptosis-mediated (PAM) process that selectively removes precancerous and other aberrant cells (Scott and Di Palma 2006), and induced immune functions (Liu 2003(Liu , 2007 have been found to be key components to the low-dose radiation ANP. Here we refer to the epigenetic PAM process as epiapoptosis.…”

“…The level of protection appears to increase as the gamma-ray contribution to the dose increases, which depends on neutron energy (Rithidech and Scott 2008). The PAM process is transient and may not persist for more than a few tens of hours (Scott and Di Palma 2006).…”

“…The current risk model for radiation-induced cancer developed at our Institute (Scott and Di Palma 2006) does not allow for different threshold distributions for the different contributors to adaptive protection. Onsets and durations of protective signaling are also not addressed.…”

“…New modeling results are also presented related to lung cancer suppression in association with residential exposure to radon progeny. The new results are based on data from a recent well-designed epidemiological study (Thompson et al 2008) and a revised version of an existing dose-response model (Scott and Di Palma 2006) that accounts for radiation adaptive responses. In the revised version, radiation-induced lung cancer is linked to radiation-induced epireprogramming of adaptive-response genes.…”